Electrosurgical systems and methods for treating tissue

ABSTRACT

Electrosurgical methods and apparatus for removing tissue from a target site of a patient, the apparatus including a probe adapted for coupling to a power supply. The electrosurgical probe includes a shaft having a first electrode type and a second electrode type. The electrosurgical apparatus/probe lacks a dedicated return electrode. Instead, the first electrode type and the second electrode type alternate between serving as active electrode and serving as return electrode. The first electrode type comprises at least one ablation electrode adapted for aggressively removing tissue from a target site. The second electrode type comprises at least one digestion electrode adapted for aggressively digesting resected tissue fragments present in an aspiration stream. The apparatus may shift from a first mode of operation wherein the first electrode type serves as active electrode, to a second mode of operation wherein the second electrode type serves as active electrode, and back to the first mode of operation, without operator input. Such a shift may be determined by the presence or absence of tissue at the first and second electrode types, or by a change in electrical impedance in the milieu of the second electrode type, and such a shift may be dependent on a suitable surface area ratio of the first electrode type to the second electrode type. The probe may include an aspiration device which accommodates an aspiration stream emanating from the target site, and a fluid delivery device for delivering an extraneous electrically conductive fluid to the probe or to the target site.

RELATED APPLICATIONS

The present invention claims priority from Provisional PatentApplication No. 60/233,345 filed Sep. 18, 2000 and Provisional PatentApplication No. 60/210,567 filed Jun. 9, 2000, which is acontinuation-in-part of U.S. patent application Ser. No. 09/197,013,filed Nov. 20, 1998 which is a continuation-in-part of U.S. patentapplication Ser. No. 09/010,382, filed Jan. 21, 1998 U.S. Pat. No.6,190,381, which is a continuation-in-part of U.S. patent applicationSer. No. 08/990,374, filed on Dec. 15, 1997 U.S. Pat. No. 6,109,268,which is a continuation-in-part of U.S. patent application Ser. No.08/485,219, filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281, thecomplete disclosures of which are incorporated herein by reference forall purposes.

The present invention is related to commonly assigned co-pendingProvisional Patent Application No. 60/062,997 filed on Oct. 23, 1997,non-provisional U.S. patent application Ser. No. 08/977,845, filed Nov.25, 1997, which is a continuation-in-part of application Ser. No.08/562,332, filed Nov. 22, 1995, the complete disclosures of which areincorporated herein by reference for all purposes. The present inventionis also related to U.S. patent application Ser. Nos. 09/109,219,09/058,571, 08/874,173 and 09/002,315, filed on Jun. 30, 1998, Apr. 10,1998, Jun. 13, 1997, and Jan. 2, 1998, respectively, and U.S. patentapplication Ser. No. 09/054,323, filed on Apr. 2, 1998, U.S. patentapplication Ser. No. 09/010,382, filed Jan. 21, 1998, and U.S. patentapplication Ser. No. 09/032,375, filed Feb. 27, 1998, U.S. patentapplication Ser. Nos. 08/977,845, filed on Nov. 25, 1997, 08/942,580,filed on Oct. 2, 1997, U.S. application Ser. No. 08/753,227, filed onNov. 22, 1996, U.S. application Ser. No. 08/687792, filed on Jul. 18,1996, the complete disclosures of which are incorporated herein byreference for all purposes. The present invention is also related tocommonly assigned U.S. Pat. No. 5,683,366, filed Nov. 22, 1995, thecomplete disclosure of which is incorporated herein by reference for allpurposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of electrosurgery,and more particularly to surgical devices and methods which employ highfrequency electrical energy to resect, coagulate, ablate, and aspiratecartilage, bone and other tissue, such as sinus tissue, adipose tissue,or meniscus, cartilage, and synovial tissue in a joint. The presentinvention also relates to apparatus and methods for aggressivelyremoving tissue at a target site by a cool ablation procedure andefficiently aspirating resected tissue from the target site, wherein theapparatus includes a bipolar electrosurgical probe but lacks a dedicatedreturn electrode. The present invention further relates to anelectrosurgical probe including a first type of tissue-alteringelectrode and a second type of tissue-altering electrode, wherein theprobe is designed to function according to one mode of operation withonly the first electrode type in contact with tissue, and the probe isdesigned to function in a different mode of operation with the secondelectrode type in contact with tissue.

Conventional electrosurgical methods generally reduce patient bleedingassociated with tissue cutting operations and improve the surgeon'svisibility. These electrosurgical devices and procedures, however,suffer from a number of disadvantages. For example, monopolarelectrosurgery methods generally direct electric current along a definedpath from the exposed or active electrode through the patient's body tothe return electrode, which is externally attached to a suitablelocation on the patient's skin. In addition, since the defined paththrough the patient's body has a relatively high electrical impedance,large voltage differences must typically be applied between the activeand return electrodes to generate a current suitable for cutting orcoagulation of the target tissue. This current, however, mayinadvertently flow along localized pathways in the body having lessimpedance than the defined electrical path. This situation willsubstantially increase the current flowing through these paths, possiblycausing damage to or destroying tissue along and surrounding thispathway.

Bipolar electrosurgical devices have an inherent advantage overmonopolar devices because the return current path does not flow throughthe patient beyond the immediate site of application of the bipolarelectrodes. In bipolar devices, both the active and return electrode aretypically exposed so that they may both contact tissue, therebyproviding a return current path from the active to the return electrodethrough the tissue. One drawback with this configuration, however, isthat the return electrode may cause tissue desiccation or destruction atits contact point with the patient's tissue.

Another limitation of conventional bipolar and monopolar electrosurgerydevices is that they are not suitable for the precise removal (ablation)of tissue. For example, conventional electrosurgical cutting devicestypically operate by creating a voltage difference between the activeelectrode and the target tissue, causing an electrical arc to formacross the physical gap between the electrode and tissue. At the pointof contact of the electric arcs with tissue, rapid tissue heating occursdue to high current density between the electrode and tissue. This highcurrent density causes cellular fluids to rapidly vaporize into steam,thereby producing a “cutting effect” along the pathway of localizedtissue heating. The tissue is parted along the pathway of vaporizedcellular fluid, inducing undesirable collateral tissue damage in regionssurrounding the target tissue site.

In addition, conventional electrosurgical methods are generallyineffective for ablating certain types of tissue, and in certain typesof environments within the body. For example, loose or elasticconnective tissue, such as the synovial tissue in joints, is extremelydifficult (if not impossible) to remove with conventionalelectrosurgical instruments because the flexible tissue tends to moveaway from the instrument when it is brought against this tissue. Sinceconventional techniques rely mainly on conducting current through thetissue, they are not effective when the instrument cannot be broughtadjacent to or in contact with the elastic tissue for a long enoughperiod of time to energize the electrode and conduct current through thetissue.

The use of electrosurgical procedures (both monopolar and bipolar) inelectrically conductive environments can be further problematic. Forexample, many arthroscopic procedures require flushing of the region tobe treated with isotonic saline, both to maintain an isotonicenvironment and to keep the field of view clear. However, the presenceof saline, which is a highly conductive electrolyte, can cause shortingof the active electrode(s) in conventional monopolar and bipolarelectrosurgery. Such shorting causes unnecessary heating in thetreatment environment and can further cause non-specific tissuedestruction.

Conventional electrosurgical cutting or resecting devices also tend toleave the operating field cluttered with tissue fragments that have beenremoved or resected from the target tissue. These tissue fragments makevisualization of the surgical site extremely difficult. Removing thesetissue fragments can also be problematic. Similar to synovial tissue, itis difficult to maintain contact with tissue fragments long enough toablate the tissue fragments in situ with conventional devices. To solvethis problem, the surgical site is periodically or continuouslyaspirated during the procedure. However, the tissue fragments often clogthe aspiration lumen of the suction instrument, forcing the surgeon toremove the instrument to clear the aspiration lumen or to introduceanother suction instrument, which increases the length and complexity ofthe procedure.

During certain electrosurgical procedures, for example in procedureswhich involve aspiration of relatively large volumes of fluid from atarget site, generating and maintaining a plasma from an electricallyconductive fluid in the vicinity of the active electrode can beproblematic. This situation may be exacerbated by splitting power fromthe power supply between two different types of active electrode, e.g. adistal ablation electrode adapted for tissue removal and a proximaldigestion electrode adapted for disintegrating resected tissuefragments. The present invention overcomes problems related to splittingelectric power between the two types of electrodes by having theablation and digestion electrodes alternate between serving as activeelectrode and serving as return electrode.

Furthermore, in certain electrosurgical procedures of the prior art, forexample, removal or resection of the meniscus during arthroscopicsurgery to the knee, it is customary to employ two different tissueremoval devices, namely an arthroscopic punch and a shaver. There is aneed for an electrosurgical apparatus which enables the aggressiveremoval of relatively hard tissues (e.g. fibrocartilaginous tissue) aswell as soft tissue, and which is adapted for aspirating resectedtissue, excess fluids, and ablation by-products from the surgical site.The instant invention provides a single device which can replace thepunch and the shaver of the prior art, wherein tissue may beaggressively removed according to a cool ablation procedure, andresected tissue can be efficiently removed by a combination ofaspiration from the site of tissue resection and digestion of resectedtissue fragments, wherein the resected tissue fragments are ablated inan aspiration stream by a cool ablation mechanism.

SUMMARY OF THE INVENTION

The present invention provides systems, apparatus, kits, and methods forselectively applying electrical energy to structures within or on thesurface of a patient's body. In particular, methods and apparatus areprovided for resecting, cutting, partially ablating, aspirating orotherwise removing tissue from a target site, and ablating the tissue insitu.

In one aspect, the present invention provides an electrosurgicalinstrument for treating tissue at a target site. The instrumentcomprises a shaft having a proximal portion and a distal end portion.One or more active loop electrodes are disposed at the distal end of theshaft. The loop electrodes preferably have one or more edges thatpromote high electric fields. A connector is disposed near the proximalend of the shaft for electrically coupling the active loop electrodes toa high frequency source.

The active loop electrodes typically have an exposed semicircular shapethat facilitates the removing or ablating of tissue at the target site.During the procedure, bodily fluid, non-ablated tissue fragments and/orair bubbles are aspirated from the target site to improve visualization.

At least one return electrode is preferably spaced from the activeelectrode(s) a sufficient distance to prevent arcing therebetween at thevoltages suitable for tissue removal and or heating, and to preventcontact of the return electrode(s) with the tissue. The current flowpath between the active and return electrodes may be generated byimmersing the target site within electrically conductive fluid (as istypical in arthroscopic procedures), or by directing an electricallyconductive fluid along a fluid path past the return electrode and to thetarget site (e.g., in open procedures). Alternatively, the electrodesmay be positioned within a viscous electrically conductive fluid, suchas a gel, at the target site, and submersing the active and returnelectrode(s) within the conductive gel. The electrically conductivefluid will be selected to have sufficient electrical conductivity toallow current to pass therethrough from the active to the returnelectrode(s), and such that the fluid ionizes into a plasma when subjectto sufficient electrical energy, as discussed below. In the exemplaryembodiment, the conductive fluid is isotonic saline, although otherfluids may be selected, as described in co-pending Provisional PatentApplication No. 60/098,122, filed Aug. 27, 1998 (Attorney Docket No.CB-7P), the complete disclosure of which is incorporated herein byreference.

In a specific embodiment, tissue ablation results from moleculardissociation or disintegration processes. Conventional electrosurgeryablates or cuts through tissue by rapidly heating the tissue untilcellular fluids explode, producing a cutting effect along the pathway oflocalized heating. The present invention volumetrically removes tissue,e.g., cartilage tissue, in a cool ablation process known as Coblation®,wherein thermal damage to surrounding tissue is minimized. During thisprocess, a high frequency voltage applied to the active electrode(s) issufficient to vaporize an electrically conductive fluid (e.g., gel orsaline) between the electrode(s) and the tissue. Within the vaporizedfluid, an ionized plasma is formed and charged particles (e.g.,electrons) cause the molecular breakdown or disintegration of tissuecomponents in contact with the plasma. This molecular dissociation isaccompanied by the volumetric removal of the tissue. This process can beprecisely controlled to effect the volumetric removal of tissue as thinas 10 to 50 microns with minimal heating of, or damage to, surroundingor underlying tissue structures. A more complete description of thisCoblation® phenomenon is described in commonly assigned U.S. Pat. No.5,683,366, the complete disclosure of which is incorporated herein byreference.

The present invention offers a number of advantages over conventionalelectrosurgery, microdebrider, shaver and laser techniques for removingsoft tissue in arthroscopic, sinus or other surgical procedures. Theability to precisely control the volumetric removal of tissue results ina field of tissue ablation or removal that is very defined, consistentand predictable. In one embodiment, the shallow depth of tissue heatingalso helps to minimize or completely eliminate damage to healthy tissuestructures, e.g., cartilage, bone and/or cranial nerves that are oftenadjacent the target sinus tissue. In addition, small blood vessels atthe target site are simultaneously cauterized and sealed as the tissueis removed to continuously maintain hemostasis during the procedure.This increases the surgeon's field of view, and shortens the length ofthe procedure. Moreover, since the present invention allows for the useof electrically conductive fluid (contrary to prior art bipolar andmonopolar electrosurgery techniques), isotonic saline may be used duringthe procedure. Saline is the preferred medium for irrigation because ithas the same concentration as the body's fluids and, therefore, is notabsorbed into the body as much as certain other fluids.

Systems according to the present invention generally include anelectrosurgical instrument having a shaft with proximal and distal endportions, one or more active loop electrode(s) at the distal end of theshaft and one or more return electrode(s). The system can furtherinclude a high frequency power supply for applying a high frequencyvoltage difference between the active electrode(s) and the returnelectrode(s). The instrument typically includes an aspiration lumenwithin the shaft having an opening positioned proximal of the activeelectrode(s) so as to draw bodily fluids and air bubbles into theaspiration lumen under vacuum pressure.

In another aspect, the present invention provides an electrosurgicalprobe having a fluid delivery element for delivering electricallyconductive fluid to the active electrode(s) and the target site. Thefluid delivery element may be located on the instrument, e.g., a fluidlumen or tube, or it may be part of a separate instrument. In anexemplary configuration the fluid delivery element includes at least oneopening that is positioned around the active electrodes. Such aconfiguration provides an improved flow of electrically conductive fluidand promotes more aggressive generation of the plasma at the targetsite.

Alternatively, an electrically conductive fluid, such as a gel or liquidspray, e.g., saline, may be applied to the tissue. In arthroscopicprocedures, the target site will typically already be immersed in aconductive irrigant, i.e., saline. In these embodiments, the apparatusmay lack a fluid delivery element. In both embodiments, the electricallyconductive fluid will preferably generate a current flow path betweenthe active electrode(s) and the return electrode(s). In an exemplaryembodiment, a return electrode is located on the instrument and spaced asufficient distance from the active electrode(s) to substantially avoidor minimize current shorting therebetween and to shield the tissue fromthe return electrode at the target site.

In another aspect, the present invention provides a method for applyingelectrical energy to a target site within or on a patient's body. Themethod comprises positioning one or more active electrodes into at leastclose proximity with the target site. An electrically conductive fluidis provided to the target site and a high frequency voltage is appliedbetween the active electrodes and a return electrode to generaterelatively high, localized electric field intensities between the activeelectrode(s) and the target site, wherein an electrical current flowsfrom the active electrode(s) through tissue at the target site. Theactive electrodes are moved in relation to the targeted tissue to resector ablate the tissue at the target site.

In another aspect, the present invention provides an electrosurgicalsystem for removing tissue from a target site to be treated. The systemincludes a probe and a power supply for supplying high frequencyalternating current to the probe. The probe includes a shaft, anablation electrode, and a digestion electrode, wherein the ablationelectrode and the digestion electrode are independently coupled toopposite poles of the power supply. Typically, the probe andelectrosurgical system lack a dedicated return electrode. Instead, theablation and digestion electrodes can alternate between serving asactive electrode and serving as return electrode, i.e., the power supplycan alternate between preferentially supplying electric power to theablation electrode and preferentially supplying electric power to thedigestion electrode. When power is preferentially supplied to theablation electrode, the ablation electrode functions as an activeelectrode and is capable of ablating tissue, while the digestionelectrode serves as a return electrode. When power is preferentiallysupplied to the digestion electrode, the digestion electrode functionsas an active electrode and is capable of ablating tissue, while theablation electrode serves as a return electrode. Thus, both the ablationelectrode and the digestion electrode are adapted for ablating tissue,albeit under different circumstances. Namely, the ablation electrode isadapted for removing tissue from a site targeted for treatment, whereasthe digestion electrode is adapted for digesting tissue fragmentsresected from the target site by the ablation electrode. Thus, the twoelectrode types (ablation and digestion electrodes) operate in concertto conveniently remove, ablate, or digest tissue targeted for treatment.It should be noted that the mechanism involved in removing tissue by theablation electrode and in digesting tissue fragments by the digestionelectrode may be essentially the same, e.g., a cool ablation processinvolving the molecular dissociation of tissue components to yield lowmolecular weight ablation by-products.

By the term “return electrode” is meant an electrode which serves toprovide a current flow path from an active electrode back to a powersupply, and/or an electrode of an electrosurgical device which does notproduce an electrically-induced tissue-altering effect on tissuetargeted for treatment. By the term “active electrode” is meant anelectrode of an electrosurgical device which is adapted for producing anelectrically-induced tissue-altering effect when brought into contactwith, or close proximity to, a tissue targeted for treatment.

In another aspect, the invention provides an apparatus and method fortreating tissue at a target site with an electrosurgical system having aprobe including an ablation electrode and a digestion electrode, whereinthe electrosurgical system lacks a dedicated return electrode. Theablation electrode and the digestion electrode are independently coupledto opposite poles of a power supply for supplying power to the ablationelectrode and to the digestion electrode. Typically, during operation ofthe electrosurgical system of the invention the power supply does notsupply power equally to the ablation electrode and to the digestionelectrode. Instead, at a given time point during operation of theelectrosurgical system, one of the two electrode types (the ablationelectrode(s) or the digestion electrode(s)) may receive up to about 100%of the available power from the power supply.

According to one embodiment, the probe is positioned adjacent to atissue to be treated, and power is supplied from the power supplypreferentially to the ablation electrode at the expense, or to theexclusion, of the digestion electrode. In this manner the ablationelectrode may receive up to about 100% of the power from the powersupply, resulting in efficient generation of a plasma in the vicinity ofthe ablation electrode, and removal of tissue from the target site.During this phase of the procedure, the ablation electrode obviously hasa tissue-altering effect on the tissue and functions as the activeelectrode, while the digestion electrode serves as the return electrodeand is incapable of a tissue-altering effect. During a different phaseof the procedure, power from the power supply is preferentially suppliedto the digestion electrode at the expense of the ablation electrode. Inthis manner the digestion electrode may receive up to about 100% of thepower from the power supply, resulting in efficient generation of aplasma in the vicinity of the digestion electrode, and digestion oftissue fragments resected by the ablation electrode. During the latterphase of the procedure, the digestion electrode obviously has atissue-altering effect and functions as the active electrode, while theablation electrode serves as the return electrode and is incapable of atissue-altering effect.

Shifting power delivery from the ablation electrode to the digestionelectrode, and vice versa, may be effected by the presence or absence oftissue (including whole tissue and resected tissue fragments) in contactwith, or in the vicinity of, the ablation and digestion electrodes. Forexample, when only the ablation electrode is in contact with tissue(i.e., the digestion electrode is not in contact with tissue): a) theablation electrode receives most of the available electric power fromthe power supply, and the ablation electrode functions as an activeelectrode (i.e., ablates tissue); and b) current density at thedigestion electrode decreases, and the digestion electrode functions asa return electrode (i.e., has no tissue effect, and completes a currentflow path from the ablation electrode back to the power supply).Conversely, when only the digestion electrode is in contact with tissue(i.e., the ablation electrode is not in contact with tissue): a) thedigestion electrode receives most of the available electric power fromthe power supply, and the digestion electrode functions as an activeelectrode; and b) current density at the ablation electrode decreases,and the ablation electrode functions as a return electrode (i.e., has notissue effect, and completes a current flow path from the digestionelectrode back to the power supply).

Thus, according to certain aspects of the invention, there is providedan electrosurgical probe having a first electrode type and a secondelectrode type, wherein both the first and second electrode types arecapable of serving as an active electrode and are adapted for ablatingtissue, and both the first and second electrode type are capable ofserving as a return electrode. The probe is designed to operate indifferent modes according to whether i) only the first electrode type isin contact with tissue, ii) only the second electrode type is in contactwith tissue, or iii) both the first electrode type and the secondelectrode type are in contact with tissue at the same time. Typically,the electrosurgical probe is configured such that a first electrode typecan be brought into contact with tissue at a target site while a secondelectrode type does not contact the tissue at the target site. Indeed,in some embodiments the electrosurgical probe is configured such thatone type of electrode can be brought into contact with tissue at atarget site while the other electrode type remains remote from thetissue at the target site.

In one mode of operation, both the first electrode type (ablationelectrode) and second electrode type (digestion electrode) may be incontact with tissue simultaneously. Under these circumstances, byarranging for an appropriate ablation electrode:digestion electrodesurface area ratio, the available power from the power supply may besupplied preferentially to the digestion electrode. When tissue is incontact with, or in the vicinity of, the digestion electrode, theelectrical impedance in the vicinity of the digestion electrode changes.Such a change in electrical impedance typically results from thepresence of one or more tissue fragments flowing towards the digestionelectrode in an aspiration stream comprising an electrically conductivefluid, and the change in electrical impedance may trigger a shift fromthe ablation electrode serving as active electrode to the digestionelectrode serving as active electrode. The ablation electrode may belocated distal to an aspiration port on the shaft. The digestionelectrode may be arranged in relation to an aspiration device, so thatthe aspiration stream contacts the digestion electrode.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electrosurgical system incorporatinga power supply and an electrosurgical probe for tissue ablation,resection, incision, contraction and for vessel hemostasis according tothe present invention;

FIG. 2 is a side view of an electrosurgical probe according to thepresent invention incorporating a loop electrode for resection andablation of tissue;

FIG. 3 is a cross-sectional view of the electrosurgical probe of FIG. 2;

FIG. 4 is an exploded sectional view of a distal portion of theelectrosurgical probe;

FIGS. 5A and 5B are end and cross-sectional views, respectively, of theproximal portion of the probe;

FIG. 6 illustrates a surgical kit for removing and ablating tissueaccording to the present invention;

FIG. 7 is a perspective view of another electrosurgical systemincorporating a power supply, an electrosurgical probe and a supply ofelectrically conductive fluid for delivering the fluid to the targetsite;

FIG. 8 is a side view of another electrosurgical probe according to thepresent invention incorporating aspiration electrodes for ablatingaspirated tissue fragments and/or tissue strands, such as synovialtissue;

FIG. 9 is an end view of the probe of FIG. 8;

FIG. 10 is an exploded view of a proximal portion of the electrosurgicalprobe;

FIGS. 11-13 illustrate alternative probes according to the presentinvention, incorporating aspiration electrodes;

FIG. 14 illustrates an endoscopic sinus surgery procedure, wherein anendoscope is delivered through a nasal passage to view a surgical sitewithin the nasal cavity of the patient;

FIG. 15 illustrates an endoscopic sinus surgery procedure with one ofthe probes described above according to the present invention;

FIGS. 16A and 16B illustrate a detailed view of the sinus surgeryprocedure, illustrating ablation of tissue according to the presentinvention;

FIG. 17 illustrates a procedure for treating obstructive sleepdisorders, such as sleep apnea, according to the present invention;

FIG. 18 is a perspective view of another embodiment of the presentinvention;

FIG. 19 is a side-cross-sectional view of the electrosurgical probe ofFIG. 18;

FIG. 20 is an enlarged detailed cross-sectional view of the distal endportion of the probe of FIG. 18;

FIGS. 21 and 22 show the proximal end and the distal end, respectively,of the probe of FIG. 18;

FIG. 23 illustrates a method for removing fatty tissue from the abdomen,groin or thigh region of a patient according to the present invention;

FIG. 24 illustrates a method for removing fatty tissue in the head andneck region of a patient according to the present invention.

FIG. 25 is a perspective view of yet another embodiment of the presentinvention;

FIG. 26 is a side cross-sectional view of the electrosurgical probe ofFIG. 25;

FIG. 27 is an enlarged detailed view of the distal end portion of theprobe of FIG. 25;

FIG. 28 is a perspective view of the distal portion of the probe of FIG.25;

FIG. 29 is a perspective view of an insulating member of the probe ofFIG. 25;

FIG. 30 illustrates the proximal end of the probe of FIG. 25; and

FIG. 31 is an alternative embodiment of the active electrode for theprobe of FIG. 25;

FIG. 32 shows an electrosurgical probe including a resection unit,according to another embodiment of the invention;

FIG. 33 shows a resection unit of an electrosurgical probe, theresection unit including a resection electrode on a resection electrodesupport;

FIGS. 34A-D each show an electrosurgical probe including a resectionunit, according to various embodiments of the invention;

FIG. 35A shows an electrosurgical probe including a resection unit andan aspiration device, according to the invention;

FIG. 35B shows an electrosurgical probe including a resection unit and afluid delivery device, according to one embodiment of the invention;

FIGS. 36A-F each show a resection unit having at least one resectionelectrode head arranged on a resection electrode support, according tovarious embodiments of the invention;

FIG. 37 illustrates an arrangement of a resection electrode head withrespect to the longitudinal axis of a resection unit;

FIG. 38A shows, in plan view, a resection electrode support disposed ona shaft distal end of an electrosurgical probe;

FIGS. 38B-D each show a profile of a resection electrode head on aresection electrode support;

FIGS. 39A-I each show a cross-section of a resection electrode head,according to one embodiment of the invention, as seen along the lines39A-I of FIG. 38B;

FIG. 40 shows a cross-section of a resection electrode head having anexposed cutting edge and a covered portion having an insulating layer,according to another embodiment of the invention;

FIG. 41A illustrates a distal end of an electrosurgical probe includinga plurality of resection electrode heads, according to anotherembodiment of the invention;

FIG. 41B illustrates the distal end of the electrosurgical probe of FIG.41A taken along the lines 41B—41B;

FIG. 41C illustrates the distal end of the electrosurgical probe of FIG.41A taken along the lines 41C—41C;

FIG. 42A is a sectional view of a distal end portion of anelectrosurgical shaft, according to one embodiment of the invention;

FIG. 42B illustrates the distal end of the shaft of FIG. 42A taken alongthe lines 42B—42B;

FIGS. 43A-D are side views of the shaft distal end portion of anelectrosurgical probe, according to another embodiment of the invention;

FIGS. 44A-D each show a resection unit in relation to a fluid deliverydevice, according to various embodiments of the invention;

FIG. 45 shows a shaft distal end portion of an electrosurgical probe,according to one embodiment of the invention;

FIG. 46 schematically represents a surgical kit for resection andablation of tissue, according to another embodiment of the invention;

FIGS. 47A-B schematically represent a method of performing a resectionand ablation electrosurgical procedure, according to another embodimentof the invention;

FIG. 48 schematically represents a method of making a resection andablation electrosurgical probe, according to yet another embodiment ofthe invention;

FIG. 49 is a side view of an electrosurgical probe having electrodesmounted on the distal terminus of the probe shaft, according to oneembodiment of the invention;

FIG. 50A shows a longitudinal section of a probe showing detail of theshaft and handle;

FIG. 50B is an end view of the distal terminus of the electrosurgicalprobe of FIG. 50A;

FIG. 51A shows a longitudinal section of a probe showing detail of theshaft distal end, according to another embodiment of the invention;

FIG. 51B is an end view of the distal terminus of the electrosurgicalprobe of FIG. 51A;

FIG. 52A shows a longitudinal section of a probe showing detail of theshaft distal end, according to another embodiment of the invention;

FIG. 52B is an end view of the distal terminus of the electrosurgicalprobe of FIG. 52A;

FIGS. 53A-D show side, perspective, face, and sectional views,respectively of an electrode support of an electrosurgical probe,according to another embodiment of the invention;

FIGS. 54 and 55 each show a sectional view of an electrode support of anelectrosurgical probe, according to two different embodiments of theinvention;

FIG. 56A shows a longitudinal section of the shaft distal end of anelectrosurgical probe, according to another embodiment of the invention;

FIG. 56B is an end view of the distal terminus of the electrosurgicalprobe of FIG. 56A;

FIG. 56C shows attachment of an ablation electrode to an electrodesupport;

FIG. 57A shows a longitudinal section of the shaft distal end of anelectrosurgical probe, according to another embodiment of the invention;

FIG. 57B is an end view of the distal terminus of the electrosurgicalprobe of FIG. 57A;

FIG. 58 is a perspective view of a digestion electrode of anelectrosurgical probe, according to one embodiment of the invention;

FIG. 59A shows a longitudinal section view of the shaft distal end of anelectrosurgical probe, having an electrode mounted laterally on theshaft distal end, according to another embodiment of the invention;

FIG. 59B is a plan view of the shaft distal end shown in FIG. 59A;

FIG. 60A shows a plan view of the shaft distal end of an electrosurgicalprobe, having ablation and digestion electrodes mounted laterally on theshaft distal end, according to another embodiment of the invention;

FIG. 60B shows a transverse cross-section of the shaft distal end ofFIG. 60A; and

FIG. 61 schematically represents a series of steps involved in a methodof aggressively removing tissue during a surgical procedure.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention provides systems and methods for selectivelyapplying electrical energy to a target location within or on a patient'sbody. The present invention is particularly useful in procedures wherethe tissue site is flooded or submerged with an electrically conductivefluid, such as arthroscopic surgery of the knee, shoulder, ankle, hip,elbow, hand or foot. In addition, tissues which may be treated by thesystem and method of the present invention include, but are not limitedto, prostate tissue and leiomyomas (fibroids) located within the uterus,gingival tissues and mucosal tissues located in the mouth, tumors, scartissue, myocardial tissue, collagenous tissue within the eye orepidermal and dermal tissues on the surface of the skin. Otherprocedures for which the present invention may be used includelaminectomy/disketomy procedures for treating herniated disks,decompressive laminectomy for stenosis in the lumbosacral and cervicalspine, posterior lumbosacral and cervical spine fusions, treatment ofscoliosis associated with vertebral disease, foraminotomies to removethe roof of the intervertebral foramina to relieve nerve rootcompression, as well as anterior cervical and lumbar diskectomies. Thepresent invention is also useful for resecting tissue within accessiblesites of the body that are suitable for electrode loop resection, suchas the resection of prostate tissue, leiomyomas (fibroids) locatedwithin the uterus, and other diseased tissue within the body.

The present invention is also useful for procedures in the head andneck, such as the ear, mouth, pharynx, larynx, esophagus, nasal cavityand sinuses. These procedures may be performed through the mouth or noseusing speculae or gags, or using endoscopic techniques, such asfunctional endoscopic sinus surgery (FESS). These procedures may includethe removal of swollen tissue, chronically-diseased inflamed andhypertrophic mucus linings, polyps and/or neoplasms from the variousanatomical sinuses of the skull, the turbinates and nasal passages, inthe tonsil, adenoid, epi-glottic and supra-glottic regions, and salivaryglands, submucus resection of the nasal septum, excision of diseasedtissue and the like. In other procedures, the present invention may beuseful for collagen shrinkage, ablation and/or hemostasis in proceduresfor treating snoring and obstructive sleep apnea (e.g., soft palate,such as the uvula, or tongue/pharynx stiffening, and midlineglossectomies), for gross tissue removal, such as tonsillectomies,adenoidectomies, tracheal stenosis and vocal cord polyps and lesions, orfor the resection or ablation of facial tumors or tumors within themouth and pharynx, such as glossectomies, laryngectomies, acousticneuroma procedures and nasal ablation procedures. In addition, thepresent invention is useful for procedures within the ear, such asstapedotomies, tympanostomies or the like.

The present invention may also be useful for cosmetic and plasticsurgery procedures in the head and neck. For example, the presentinvention is particularly useful for ablation and sculpting of cartilagetissue, such as the cartilage within the nose that is sculpted duringrhinoplasty procedures. The present invention may also be employed forskin tissue removal and/or collagen shrinkage in the epidermis or dermistissue in the head and neck, e.g., the removal of pigmentations,vascular lesions (e.g., leg veins), scars, tattoos, etc., and for othersurgical procedures on the skin, such as tissue rejuvenation, cosmeticeye procedures (blepharoplasties), wrinkle removal, tightening musclesfor facelifts or browlifts, hair removal and/or transplant procedures,etc.

For convenience, certain embodiments of the invention will be describedprimarily with respect to the resection and/or ablation of the meniscusand the synovial tissue within a joint during an arthroscopic procedureand to the ablation, resection and/or aspiration of sinus tissue duringan endoscopic sinus surgery procedure, but it will be appreciated thatthe systems and methods can be applied equally well to proceduresinvolving other tissues of the body, as well as to other proceduresincluding open procedures, intravascular procedures, urology,laparoscopy, arthroscopy, thoracoscopy or other cardiac procedures,dermatology, orthopedics, gynecology, otorhinolaryngology, spinal andneurologic procedures, oncology, and the like.

In the present invention, high frequency (RF) electrical energy isapplied to one or more active electrodes in the presence of electricallyconductive fluid to remove and/or modify the structure of tissuestructures. Depending on the specific procedure, the present inventionmay be used to: (1) volumetrically remove tissue, bone or cartilage(i.e., ablate or effect molecular dissociation of the tissue structure);(2) cut or resect tissue; (3) shrink or contract collagen connectivetissue; and/or (4) coagulate severed blood vessels.

In one aspect of the invention, systems and methods are provided for thevolumetric removal or ablation of tissue structures. In theseprocedures, a high frequency voltage difference is applied between oneor more active electrode(s) and one or more return electrode(s) todevelop high electric field intensities in the vicinity of the targettissue site. The high electric field intensities lead to electric fieldinduced molecular breakdown of target tissue through moleculardissociation (rather than thermal evaporation or carbonization).Applicant believes that the tissue structure is volumetrically removedthrough molecular disintegration of larger organic molecules intosmaller molecules and/or atoms, such as hydrogen, oxides of carbon,hydrocarbons and nitrogen compounds. This molecular disintegrationcompletely removes the tissue structure, as opposed to dehydrating thetissue material by the removal of liquid from within the cells of thetissue, as is typically the case with electrosurgical desiccation andvaporization.

The high electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize an electricallyconductive fluid over at least a portion of the active electrode(s) inthe region between the distal tip of the active electrode(s) and thetarget tissue. The electrically conductive fluid may be a gas or liquid,such as isotonic saline, delivered to the target site, or a viscousfluid, such as a gel, that is located at the target site. In the latterembodiment, the active electrode(s) are submersed in the electricallyconductive gel during the surgical procedure. Since the vapor layer orvaporized region has a relatively high electrical impedance, itminimizes the current flow into the electrically conductive fluid. Thisionization, under optimal conditions, induces the discharge of energeticelectrons and photons from the vapor layer to the surface of the targettissue. A more detailed description of this cold ablation phenomenon,termed Coblation®, can be found in commonly assigned U.S. Pat. No.5,683,366 the complete disclosure of which is incorporated herein byreference.

The present invention applies high frequency (RF) electrical energy inan electrically conductive fluid environment to remove (i.e., resect,cut, or ablate) or contract a tissue structure, and to seal transectedvessels within the region of the target tissue. The present invention isparticularly useful for sealing larger arterial vessels, e.g., on theorder of 1 mm in diameter or greater. In some embodiments, a highfrequency power supply is provided having an ablation mode, wherein afirst voltage is applied to an active electrode sufficient to effectmolecular dissociation or disintegration of the tissue, and acoagulation mode, wherein a second, lower voltage is applied to anactive electrode (either the same or a different electrode) sufficientto achieve hemostasis of severed vessels within the tissue. In otherembodiments, an electrosurgical probe is provided having one or morecoagulation electrode(s) configured for sealing a severed vessel, suchas an arterial vessel, and one or more active electrodes configured foreither contracting the collagen fibers within the tissue or removing(ablating) the tissue, e.g., by applying sufficient energy to the tissueto effect molecular dissociation. In the latter embodiments, thecoagulation electrode(s) may be configured such that a single voltagecan be applied to coagulate tissue with the coagulation electrode(s),and to ablate or contract the tissue with the active electrode(s). Inother embodiments, the power supply is combined with the probe such thatthe coagulation electrode receives power when the power supply is in thecoagulation mode (low voltage), and the active electrode(s) receivepower when the power supply is in the ablation mode (higher voltage).

In the method of the present invention, one or more active electrodesare brought into close proximity to tissue at a target site, and thepower supply is activated in the ablation mode such that sufficientvoltage is applied between the active electrodes and the returnelectrode to volumetrically remove the tissue through moleculardissociation, as described below. During this process, vessels withinthe tissue will be severed. Smaller vessels will be automatically sealedwith the system and method of the present invention. Larger vessels, andthose with a higher flow rate, such as arterial vessels, may not beautomatically sealed in the ablation mode. In these cases, the severedvessels may be sealed by activating a control (e.g., a foot pedal) toreduce the voltage of the power supply and to convert the system intothe coagulation mode. In this mode, the active electrodes may be pressedagainst the severed vessel to provide sealing and/or coagulation of thevessel. Alternatively, a coagulation electrode located on the same or adifferent probe may be pressed against the severed vessel. Once thevessel is adequately sealed, the surgeon activates a control (e.g.,another foot pedal) to increase the voltage of the power supply andconvert the system back into the ablation mode.

The present invention is particularly useful for removing or ablatingtissue around nerves, such as spinal or cranial nerves, e.g., theolfactory nerve on either side of the nasal cavity, the optic nervewithin the optic and cranial canals, and the palatine nerve within thenasal cavity, soft palate, uvula and tonsil, etc. One of the significantdrawbacks with prior art microdebriders and lasers is that these devicesdo not differentiate between the target tissue and the surroundingnerves or bone. Therefore, the surgeon must be extremely careful duringthese procedures to avoid damage to the bone or nerves within and aroundthe nasal cavity. In the present invention, the Coblation® process forremoving tissue results in extremely small depths of collateral tissuedamage as discussed above. This allows the surgeon to remove tissueclose to a nerve without causing collateral damage to the nerve fibers.

In addition to the generally precise nature of the novel mechanisms ofthe present invention, applicant has discovered an additional method ofensuring that adjacent nerves are not damaged during tissue removal.According to the present invention, systems and methods are provided fordistinguishing between the fatty tissue immediately surrounding nervefibers and the normal tissue that is to be removed during the procedure.Peripheral nerves usually comprise a connective tissue sheath, orepineurium, enclosing the bundles of nerve fibers to protect these nervefibers. This protective tissue sheath typically comprises a fatty tissue(e.g., adipose tissue) having substantially different electricalproperties than the normal target tissue, such as the turbinates,polyps, mucus tissue or the like, that are, for example, removed fromthe nose during sinus procedures. The system of the present inventionmeasures the electrical properties of the tissue at the tip of the probewith one or more active electrode(s). These electrical properties mayinclude electrical conductivity at one, several or a range offrequencies (e.g., in the range from 1 kHz to 100 MHz), dielectricconstant, capacitance or combinations of these. In this embodiment, anaudible signal may be produced when the sensing electrode(s) at the tipof the probe detects the fatty tissue surrounding a nerve, or directfeedback control can be provided to only supply power to the activeelectrode(s), either individually or to the complete array ofelectrodes, if and when the tissue encountered at the tip or working endof the probe is normal tissue based on the measured electricalproperties.

In one embodiment, the current limiting are configured such that theactive electrodes will shut down or turn off when the electricalimpedance of tissue at the tip of the probe reaches a threshold level.When this threshold level is set to the impedance of the fatty tissuesurrounding nerves, the active electrodes will shut off whenever theycome in contact with, or in close proximity to, nerves. Meanwhile, theother active electrodes, which are in contact with or in close proximityto nasal tissue, will continue to conduct electric current to the returnelectrode. This selective ablation or removal of lower impedance tissuein combination with the Coblation® mechanism of the present inventionallows the surgeon to precisely remove tissue around nerves or bone.

In addition to the above, applicant has discovered that the Coblation®mechanism of the present invention can be manipulated to ablate orremove certain tissue structures, while having little effect on othertissue structures. As discussed above, the present invention uses atechnique of vaporizing electrically conductive fluid to form a plasmalayer or pocket around the active electrode(s), and then inducing thedischarge of energy from this plasma or vapor layer to break themolecular bonds of the tissue structure. Based on initial experiments,applicants believe that the free electrons within the ionized vaporlayer are accelerated in the high electric fields near the electrodetip(s). When the density of the vapor layer (or within a bubble formedin the electrically conductive liquid) becomes sufficiently low (i.e.,less than approximately 10²⁰ atoms/cm³ for aqueous solutions), theelectron mean free path increases to enable subsequently injectedelectrons to cause impact ionization within these regions of low density(i.e., vapor layers or bubbles). Energy evolved by the energeticelectrons (e.g., 4 to 5 eV) can subsequently bombard a molecule andbreak its bonds, dissociating a molecule into free radicals, which thencombine to form gaseous or liquid Coblation® by-products.

The energy evolved by the energetic electrons may be varied by adjustinga variety of factors, such as: the number of active electrodes;electrode size and spacing; electrode surface area; asperities and sharpedges on the electrode surfaces; electrode materials; applied voltageand power; current limiting means, such as inductors; electricalconductivity of the fluid in contact with the electrodes; density of thefluid; and other factors. Accordingly, these factors can be manipulatedto control the energy level of the excited electrons. Since differenttissue structures have different molecular bonds, the present inventioncan be configured to break the molecular bonds of certain tissue, whilehaving too low an energy to break the molecular bonds of other tissue.For example, components of adipose tissue have double bonds that requirea substantially higher energy level than 4 to 5 eV to break.Accordingly, the present invention in its current configurationgenerally does not ablate or remove such fatty tissue. However, thepresent invention may be used to effectively ablate cells to release theinner fat content in a liquid form. Of course, factors may be changedsuch that these double bonds can be broken (e.g., increasing the voltageor changing the electrode configuration to increase the current densityat the electrode tips).

In another aspect of the invention, a loop electrode is employed toresect, shape or otherwise remove tissue fragments from the treatmentsite, and one or more active electrodes are employed to ablate (i.e.,break down the tissue by processes including molecular dissociation ordisintegration) the non-ablated tissue fragments in situ. Once a tissuefragment is cut, partially ablated or resected by the loop electrode,one or more active electrodes will be brought into close proximity tothese fragments (either by moving the probe into position, or by drawingthe fragments to the active electrodes with a suction lumen). Voltage isapplied between the active electrodes and the return electrode tovolumetrically remove the fragments through molecular dissociation, asdescribed above. The loop electrode and the active electrodes arepreferably electrically isolated from each other such that, for example,current can be limited (passively or actively) or completely interruptedto the loop electrode as the surgeon employs the active electrodes toablate tissue fragments (and vice versa).

In another aspect of the invention, the loop electrode(s) are employedto ablate tissue using the Coblation® mechanisms described above. Inthese embodiments, the loop electrode(s) provides a relatively uniformsmooth cutting or ablation effect across the tissue. In addition, loopelectrodes generally have a larger surface area exposed to electricallyconductive fluid (as compared to the smaller active electrodes describedabove), which increases the rate of ablation of tissue. Preferably, theloop electrode(s) extend a sufficient distance from the electrodesupport member selected to achieve a desirable ablation rate, whileminimizing power dissipation into the surrounding medium (which couldcause undesirable thermal damage to surrounding or underlying tissue).In an exemplary embodiment, the loop electrode has a length from one endto the other end of about 0.5 to 20 mm, usually about 1 to 8 mm. Theloop electrode usually extends about 0.25 to 10 mm from the distal endof the support member, preferably about 1 to 4 mm.

The loop electrode(s) may have a variety of cross-sectional shapes.Electrode shapes according to the present invention can include the useof formed wire (e.g., by drawing round wire through a shaping die) toform electrodes with a variety of cross-sectional shapes, such assquare, rectangular, L or V shaped, or the like. Electrode edges mayalso be created by removing a portion of the elongate metal electrode toreshape the cross-section. For example, material can be removed alongthe length of a solid or hollow wire electrode to form D or C shapedwires, respectively, with edges facing in the cutting direction.Alternatively, material can be removed at closely spaced intervals alongthe electrode length to form transverse grooves, slots, threads or thelike along the electrodes.

In some embodiments, the loop electrode(s) will have a “non-active”portion or surface to selectively reduce undesirable current flow fromthe non-active portion or surface into tissue or surroundingelectrically conductive liquids (e.g., isotonic saline, blood orblood/non-conducting irrigant mixtures). Preferably, the “non-active”electrode portion will be coated with an electrically insulatingmaterial. This can be accomplished, for example, with plasma depositedcoatings of an insulating material, thin-film deposition of aninsulating material using evaporative or sputtering techniques (e.g.,SiO₂ or Si₃N₄), dip coating, or by providing an electrically insulatingsupport member to electrically insulate a portion of the externalsurface of the electrode. The electrically insulated non-active portionof the active electrode(s) allows the surgeon to selectively resectand/or ablate tissue, while minimizing necrosis or ablation ofsurrounding non-target tissue or other body structures.

In addition, the loop electrode(s) may comprise a single electrodeextending from first and second ends to an insulating support in theshaft, or multiple, electrically isolated electrodes extending aroundthe loop. One or more return electrodes may also be positioned along theloop portion. Further descriptions of these configurations can be foundin U.S. application Ser. No. 08/687792, filed on Jul. 18, 1996 (DocketNo. 16238-001600), which as already been incorporated herein byreference.

The electrosurgical probe will comprise a shaft or a handpiece having aproximal end and a distal end which supports one or more activeelectrode(s). The shaft or handpiece may assume a wide variety ofconfigurations, with the primary purpose being to mechanically supportthe active electrode and permit the treating physician to manipulate theelectrode from a proximal end of the shaft. The shaft may be rigid orflexible, with flexible shafts optionally being combined with agenerally rigid external tube for mechanical support. The distal portionof the shaft may comprise a flexible material, such as plastics,malleable stainless steel, etc, so that the physician can mold thedistal portion into different configurations for different applications.Flexible shafts may be combined with pull wires, shape memory actuators,and other known mechanisms for effecting selective deflection of thedistal end of the shaft to facilitate positioning of the electrodearray. The shaft will usually include a plurality of wires or otherconductive elements running axially therethrough to permit connection ofthe electrode array to a connector at the proximal end of the shaft.Thus, the shaft will typically have a length of at least 5 cm for oralprocedures and at least 10 cm, more typically being 20 cm, or longer forendoscopic procedures. The shaft will typically have a diameter of atleast 0.5 mm and frequently in the range of from about 1 to 10 mm. Ofcourse, for dermatological procedures on the outer skin, the shaft mayhave any suitable length and diameter that would facilitate handling bythe surgeon.

For procedures within the nose and joints, the shaft will have asuitable diameter and length to allow the surgeon to reach the target bydelivering the probe shaft through an percutaneous opening in thepatient (e.g., a portal formed in the joint in arthroscopic surgery, orthrough one of the patient's nasal passages in FESS). Thus, the shaftwill usually have a length in the range of from about 5 to 25 cm, and adiameter in the range of from about 0.5 to 5 mm. For proceduresrequiring the formation of a small hole or channel in tissue, such astreating swollen turbinates, the shaft diameter will usually be lessthan 3 mm, preferably less than about 1 mm. Likewise, for procedures inthe ear, the shaft should have a length in the range of about 3 to 20cm, and a diameter of about 0.3 to 5 mm. For procedures in the mouth orupper throat, the shaft will have any suitable length and diameter thatwould facilitate handling by the surgeon. For procedures in the lowerthroat, such as laryngectomies, the shaft will be suitably designed toaccess the larynx. For example, the shaft may be flexible, or have adistal bend to accommodate the bend in the patient's throat. In thisregard, the shaft may be a rigid shaft having a specifically designedbend to correspond with the geometry of the mouth and throat, or it mayhave a flexible distal end, or it may be part of a catheter. In any ofthese embodiments, the shaft may also be introduced through rigid orflexible endoscopes. Specific shaft designs will be described in detailin connection with the figures hereinafter.

The current flow path between the active electrode(s) and the returnelectrode(s) may be generated by submerging the tissue site in anelectrically conductive fluid (e.g., a viscous fluid, such as anelectrically conductive gel), or by directing an electrically conductivefluid along a fluid path to the target site (i.e., a liquid, such asisotonic saline, or a gas, such as argon). This latter method isparticularly effective in a dry environment (i.e., the tissue is notsubmerged in fluid) because the electrically conductive fluid provides asuitable current flow path from the active electrode to the returnelectrode. A more complete description of an exemplary method ofdirecting electrically conductive fluid between the active and returnelectrodes is described in parent application Ser. No. 08/485,219, filedJun. 7, 1995 (Attorney Docket No. 16238-000600), previously incorporatedherein by reference.

In some procedures, it may also be necessary to retrieve or aspirate theelectrically conductive fluid after it has been directed to the targetsite. For example, in procedures in the nose, mouth or throat, it may bedesirable to aspirate the fluid so that it does not flow down thepatient's throat. In addition, it may be desirable to aspirate smallpieces of tissue that are not completely disintegrated by the highfrequency energy, air bubbles, or other fluids at the target site, suchas blood, mucus, the gaseous products of ablation, etc. Accordingly, thesystem of the present invention can include a suction lumen in theprobe, or on another instrument, for aspirating fluids from the targetsite.

In some embodiments, the probe will include one or more aspirationelectrode(s) coupled to the distal end of the suction lumen forablating, or at least reducing the volume of, tissue fragments that areaspirated into the lumen. The aspiration electrode(s) function mainly toinhibit clogging of the lumen that may otherwise occur as larger tissuefragments are drawn therein. The aspiration electrode(s) may bedifferent from the ablation active electrode(s), or the sameelectrode(s) may serve both functions. In some embodiments, the probewill be designed to use suction force to draw loose tissue, such assynovial tissue to the aspiration or ablation electrode(s) on the probe,which are then energized to ablate the loose tissue.

In other embodiments, the aspiration lumen can be positioned proximal ofthe active electrodes a sufficient distance such that the aspirationlumen will primarily aspirate air bubbles and body fluids such as blood,mucus, or the like. Such a configuration allows the electricallyconductive fluid to dwell at the target site for a longer period.Consequently, the plasma can be created more aggressively at the targetsite and the tissue can be treated in a more efficient manner.Additionally, by positioning the aspiration lumen opening somewhatdistant from the active electrodes, it may not be necessary to haveablation electrodes at the lumen opening since, in this configuration,tissue fragments will typically not be aspirated through the lumen.

The present invention may use a single active electrode or an electrodearray distributed over a contact surface of a probe. In the latterembodiment, the electrode array usually includes a plurality ofindependently current-limited and/or power-controlled active electrodesto apply electrical energy selectively to the target tissue whilelimiting the unwanted application of electrical energy to thesurrounding tissue and environment. Such unwanted application ofelectrical energy results from power dissipation into surroundingelectrically conductive liquids, such as blood, normal saline,electrically conductive gel and the like. The active electrodes may beindependently current-limited by isolating the terminals from each otherand connecting each terminal to a separate power source that is isolatedfrom the other active electrodes. Alternatively, the active electrodesmay be connected to each other at either the proximal or distal ends ofthe probe to form a single connector that couples to a power source.

In one configuration, each individual active electrode in the electrodearray is electrically insulated from all other active electrodes in thearray within the probe and is connected to a power source which isisolated from each of the other active electrodes in the array or tocircuitry which limits or interrupts current flow to the activeelectrode when low resistivity material (e.g., blood, electricallyconductive saline irrigant or electrically conductive gel) causes alower impedance path between the return electrode and the individualactive electrode. The isolated power sources for each individual activeelectrode may be separate power supply circuits having internalimpedance characteristics which limit power to the associated activeelectrode when a low impedance return path is encountered. By way ofexample, the isolated power source may be a user selectable constantcurrent source. In this embodiment, lower impedance paths willautomatically result in lower resistive heating levels since the heatingis proportional to the square of the operating current times theimpedance. Alternatively, a single power source may be connected to eachof the active electrodes through independently actuatable switches, orby independent current limiting elements, such as inductors, capacitors,resistors and/or combinations thereof. The current limiting elements maybe provided in the probe, connectors, cable, controller or along theconductive path from the controller to the distal tip of the probe.Alternatively, the resistance and/or capacitance may occur on thesurface of the active electrode(s) due to oxide layers which formselected active electrodes (e.g., titanium or a resistive coating on thesurface of metal, such as platinum).

The tip region of the probe may comprise many independent activeelectrodes designed to deliver electrical energy in the vicinity of thetip. The selective application of electrical energy to the conductivefluid is achieved by connecting each individual active electrode and thereturn electrode to a power source having independently controlled orcurrent limited channels. The return electrode(s) may comprise a singletubular member of conductive material proximal to the electrode array atthe tip which also serves as a conduit for the supply of theelectrically conductive fluid between the active and return electrodes.Alternatively, the probe may comprise an array of return electrodes atthe distal tip of the probe (together with the active electrodes) tomaintain the electric current at the tip. The application of highfrequency voltage between the return electrode(s) and the electrodearray results in the generation of high electric field intensities atthe distal tips of the active electrodes with conduction of highfrequency current from each individual active electrode to the returnelectrode. The current flow from each individual active electrode to thereturn electrode(s) is controlled by either active or passive means, ora combination thereof, to deliver electrical energy to the surroundingconductive fluid while minimizing energy delivery to surrounding(non-target) tissue.

The application of a high frequency voltage between the returnelectrode(s) and the active electrode(s) for appropriate time intervalseffects cutting, removing, ablating, shaping, contracting or otherwisemodifying the target tissue. The tissue volume over which energy isdissipated (i.e., over which a high current density exists) may beprecisely controlled, for example, by the use of a multiplicity of smallactive electrodes whose effective diameters or principal dimensionsrange from about 5 mm to 0.01 mm, preferably from about 2 mm to 0.05 mm,and more preferably from about 1 mm to 0.1 mm. In these embodiments,electrode areas for both circular and non-circular terminals will have acontact area (per active electrode) below 25 mm², preferably being inthe range from 0.0001 mm² to 1 mm², and more preferably from 0.005 mm²to 0.5 mm². The circumscribed area of the electrode array is in therange from 0.25 mm² to 75 mm², preferably from 0.5 mm² to 40 mm², andwill usually include at least two isolated active electrodes, preferablyat least five active electrodes, often greater than 10 active electrodesand even 50 or more active electrodes, disposed over the distal contactsurfaces on the shaft. The use of small diameter active electrodesincreases the electric field intensity and reduces the extent or depthof tissue heating as a consequence of the divergence of current fluxlines which emanate from the exposed surface of each active electrode.

The area of the tissue treatment surface can vary widely, and the tissuetreatment surface can assume a variety of geometries, with particularareas and geometries being selected for specific applications. Activeelectrode surfaces can have areas in the range from 0.25 mm² to 75 mm²,usually being from about 0.5 mm² to 40 mm². The geometries can beplanar, concave, convex, hemispherical, conical, linear “in-line” arrayor virtually any other regular or irregular shape. Most commonly, theactive electrode(s) or active electrode(s) will be formed at the distaltip of the electrosurgical probe shaft, frequently being planar,disk-shaped, or hemispherical surfaces for use in reshaping proceduresor being linear arrays for use in cutting. Alternatively oradditionally, the active electrode(s) may be formed on lateral surfacesof the electrosurgical probe shaft (e.g., in the manner of a spatula),facilitating access to certain body structures in endoscopic procedures.

The electrically conductive fluid should have a threshold conductivityto provide a suitable conductive path between the active electrode(s)and the return electrode(s). The electrical conductivity of the fluid(in units of millisiemens per centimeter or mS/cm) will usually begreater than 0.2 mS/cm, preferably will be greater than 2 mS/cm and morepreferably greater than 10 mS/cm. In an exemplary embodiment, theelectrically conductive fluid is isotonic saline, which has aconductivity of about 17 mS/cm.

In some embodiments, the electrode support and the fluid outlet may berecessed from an outer surface of the probe or handpiece to confine theelectrically conductive fluid to the region immediately surrounding theelectrode support. In addition, the shaft may be shaped so as to form acavity around the electrode support and the fluid outlet. This helps toassure that the electrically conductive fluid will remain in contactwith the active electrode(s) and the return electrode(s) to maintain theconductive path therebetween. In addition, this will help to maintain avapor or plasma layer between the active electrode(s) and the tissue atthe treatment site throughout the procedure, which reduces the thermaldamage that might otherwise occur if the vapor layer were extinguisheddue to a lack of conductive fluid. Provision of the electricallyconductive fluid around the target site also helps to maintain thetissue temperature at desired levels.

The voltage applied between the return electrode(s) and the electrodearray will be at high or radio frequency, typically between about 5 kHzand 20 MHz, usually being between about 30 kHz and 2.5 MHz, preferablybeing between about 50 kHz and 500 kHz, more preferably less than 350kHz, and most preferably between about 100 kHz and 200 kHz. The RMS(root mean square) voltage applied will usually be in the range fromabout 5 volts to 1000 volts, preferably being in the range from about 10volts to 500 volts depending on the active electrode size, the operatingfrequency and the operation mode of the particular procedure or desiredeffect on the tissue (i.e., contraction, coagulation or ablation).Typically, the peak-to-peak voltage will be in the range of 10 to 2000volts, preferably in the range of 20 to 1200 volts and more preferablyin the range of about 40 to 800 volts (again, depending on the electrodesize, the operating frequency and the operation mode).

As discussed above, the voltage is usually delivered in a series ofvoltage pulses or alternating current of time varying voltage amplitudewith a sufficiently high frequency (e.g., on the order of 5 kHz to 20MHz) such that the voltage is effectively applied continuously (ascompared with e.g., lasers claiming small depths of necrosis, which aregenerally pulsed at about 10 to 20 Hz). In addition, the duty cycle(i.e., cumulative time in any one-second interval that energy isapplied) is on the order of about 50% for the present invention, ascompared with pulsed lasers which typically have a duty cycle of about0.0001%.

The preferred power source of the present invention delivers a highfrequency current selectable to generate average power levels rangingfrom several milliwatts to tens of watts per electrode, depending on thevolume of target tissue being heated, and/or the maximum allowedtemperature selected for the probe tip. The power source allows the userto select the voltage level according to the specific requirements of aparticular FESS procedure, arthroscopic surgery, dermatologicalprocedure, ophthalmic procedures, open surgery or other endoscopicsurgery procedure. A description of a suitable power source can be foundin “Systems and Methods for Electrosurgical Tissue and FluidCoagulation,” filed on Oct. 23, 1997 (Attorney Docket No. 16238-007400),the complete disclosure of which has been incorporated herein byreference.

The power source may be current limited or otherwise controlled so thatundesired heating of the target tissue or surrounding (non-target)tissue does not occur. In one embodiment of the present invention,current limiting inductors are placed in series with each independentactive electrode, where the inductance of the inductor is in the rangeof 10 uH to 50,000 uH, depending on the electrical properties of thetarget tissue, the desired tissue heating rate and the operatingfrequency. Alternatively, capacitor-inductor (LC) circuit structures maybe employed, as described previously in co-pending PCT application No.PCT/US94/05168, the complete disclosure of which is incorporated hereinby reference. Additionally, current limiting resistors may be selected.Preferably, these resistors will have a large positive temperaturecoefficient of resistance so that, as the current level begins to risefor any individual active electrode in contact with a low resistancemedium (e.g., saline irrigant or conductive gel), the resistance of thecurrent limiting resistor increases significantly, thereby minimizingthe power delivery from the active electrode into the low resistancemedium (e.g., saline irrigant or conductive gel).

It should be clearly understood that the invention is not limited toelectrically isolated active electrodes, or even to a plurality ofactive electrodes. For example, the array of active electrodes may beconnected to a single lead that extends through the probe shaft to apower source of high frequency current. Alternatively, the probe mayincorporate a single electrode that extends directly through the probeshaft or is connected to a single lead that extends to the power source.The active electrode may have a ball shape (e.g., for tissuevaporization and desiccation), a twizzle shape (for vaporization andneedle-like cutting), a spring shape (for rapid tissue debulking anddesiccation), a twisted metal shape, an annular or solid tube shape orthe like. Alternatively, the electrode may comprise a plurality offilaments, a rigid or flexible brush electrode (for debulking a tumor,such as a fibroid, bladder tumor or a prostate adenoma), a side-effectbrush electrode on a lateral surface of the shaft, a coiled electrode orthe like. In one embodiment, the probe comprises a single activeelectrode that extends from an insulating member, e.g., ceramic, at thedistal end of the probe. The insulating member is preferably a tubularstructure that separates the active electrode from a tubular or annularreturn electrode positioned proximal to the insulating member and theactive electrode.

Referring now to FIG. 1, an exemplary electrosurgical system 5 forresection, ablation, coagulation and/or contraction of tissue will nowbe described in detail. As shown, electrosurgical system 5 generallyincludes an electrosurgical probe 20 connected to a power supply 10 forproviding high frequency voltage to one or more active electrodes and aloop electrode (not shown in FIG. 1) on probe 20. Probe 20 includes aconnector housing 44 at its proximal end, which can be removablyconnected to a probe receptacle 32 of a probe cable 22. The proximalportion of cable 22 has a connector 34 to couple probe 20 to powersupply 10. Power supply 10 has an operator controllable voltage leveladjustment 38 to change the applied voltage level, which is observableat a voltage level display 40. Power supply 10 also includes one or morefoot pedals 24 and a cable 26 which is removably coupled to a receptacle30 with a cable connector 28. The foot pedal 24 may also include asecond pedal (not shown) for remotely adjusting the energy level appliedto active electrodes 104 (FIG. 2), and a third pedal (also not shown)for switching between an ablation mode and a coagulation mode.

FIGS. 2-5 illustrate an exemplary electrosurgical probe 20 constructedaccording to the principles of the present invention. As shown in FIG.2, probe 20 generally includes an elongated shaft 100 which may beflexible or rigid, a handle 204 coupled to the proximal end of shaft 100and an electrode support member 102 coupled to the distal end of shaft100. Shaft 100 preferably comprises an electrically conducting material,usually metal, which is selected from the group consisting of tungsten,stainless steel alloys, platinum or its alloys, titanium or its alloys,molybdenum or its alloys, and nickel or its alloys. Shaft 100 includesan electrically insulating jacket 108, which is typically formed as oneor more electrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulating jacket over the shaft prevents direct electricalcontact between these metal elements and any adjacent body structure orthe surgeon. Such direct electrical contact between a body structure(e.g., tendon) and an exposed electrode could result in unwanted beatingof the structure at the point of contact causing necrosis.

Handle 204 typically comprises a plastic material that is easily moldedinto a suitable shape for handling by the surgeon. As shown in FIG. 3,handle 204 defines an inner cavity 208 that houses electricalconnections 250 (discussed below), and provides a suitable interface forconnection to an electrical connecting cable 22 (see FIG. 1). As shownin FIG. 5B, the probe will also include a coding resistor 400 having avalue selected to program different output ranges and modes of operationfor the power supply. This allows a single power supply to be used witha variety of different probes in different applications (e.g.,dermatology, cardiac surgery, neurosurgery, arthroscopy, etc). Electrodesupport member 102 extends from the distal end of shaft 100 (usuallyabout 1 to 20 mm), and provides support for a loop electrode 103 and aplurality of electrically isolated active electrodes 104 (see FIG. 4).

As shown in FIG. 3, the distal portion of shaft 100 is preferably bentto improve access to the operative site of the tissue being treated(e.g., contracted). Electrode support member 102 has a substantiallyplanar tissue treatment surface 212 (see FIG. 4) that is usually at anangle of about 10 to 90 degrees relative to the longitudinal axis ofshaft 100, preferably about 10 to 30 degrees and more preferably about15-18 degrees. In addition, the distal end of the shaft may have abevel, as described in commonly-assigned patent application Ser. No.08/562,332 filed Nov. 22, 1995 (Attorney Docket 16238-000710). Inalternative embodiments, the distal portion of shaft 100 comprises aflexible material which can be deflected relative to the longitudinalaxis of the shaft. Such deflection may be selectively induced bymechanical tension of a pull wire, for example, or by a shape memorywire that expands or contracts by externally applied temperaturechanges. A more complete description of this embodiment can be found inPCT International Application, U.S. National Phase Ser. No.PCT/US94/05168.

The bend in the distal portion of shaft 100 is particularly advantageousin arthroscopic treatment of joint tissue as it allows the surgeon toreach the target tissue within the joint as the shaft 100 extendsthrough a cannula or portal. Of course, it will be recognized that theshaft may have different angles depending on the procedure. For example,a shaft having a 90° bend angle may be particularly useful for accessingtissue located in the back portion of a joint compartment and a shafthaving a 10° to 30° bend angle may be useful for accessing tissue nearor in the front portion of the joint compartment.

As shown in FIG. 4, loop electrode 103 has first and second endsextending from the electrode support member 102. The first and secondends are coupled to, or integral with, a pair of connectors 300, 302,e.g., wires, that extend through the shaft of the probe to its proximalend for coupling to the high frequency power supply. The loop electrodeusually extends about 0.5 to about 10 mm from the distal end of supportmember 102, preferably about 1 to 2 mm. In the representativeembodiment, the loop electrode has a solid construction with asubstantially uniform cross-sectional area, e.g., circular, square, etc.Of course, it will be recognized that the loop or ablation electrode mayhave a wide variety of cross-sectional shapes, such as annular, square,rectangular, L-shaped, V-shaped, D-shaped, C-shaped, star-shaped andcrossed-shaped, as described in commonly-assigned co-pending patentapplication Ser. No. 08/687792. In addition, it should be noted thatloop electrode 103 may have a geometry other than that shown in FIGS.2-5, such as a semi-circular loop, a V-shaped loop, a straight wireelectrode extending between two support members, and the like. Also,loop electrode may be positioned on a lateral surface of the shaft, orit may extend at a transverse angle from the distal end of the shaft,depending on the particular surgical procedure.

Loop electrode 103 usually extends further away from the support memberthan the active electrodes 104 to facilitate resection and ablation oftissue. As discussed below, loop electrode 103 is especially configuredfor resecting fragments or pieces of tissue, while the active electrodesablate or cause molecular dissociation or disintegration of the removedpieces from the fluid environment. In the presently preferredembodiment, the probe will include 3 to 7 active electrodes positionedon either side of the loop electrode. The probe may further include asuction lumen (not shown) for drawing the pieces of tissue toward theactive electrodes after they have been removed from the target site bythe loop electrode 103.

Referring to FIG. 4, the electrically isolated active electrodes 104 arepreferably spaced apart over tissue treatment surface 212 of electrodesupport member 102. The tissue treatment surface and individual activeelectrodes 104 will usually have dimensions within the ranges set forthabove. In the representative embodiment, the tissue treatment surface212 has an oval cross-sectional shape with a length L in the range of 1mm to 20 mm and a width W in the range from 0.3 mm to 7 mm. The ovalcross-sectional shape accommodates the bend in the distal portion ofshaft 202. The active electrodes 104 preferably extend slightly outwardfrom surface 212, typically by a distance from 0.2 mm to 2. However, itwill be understood that electrodes 104 may be flush with this surface,or even recessed, if desired. In one embodiment of the invention, theactive electrodes are axially adjustable relative to the tissuetreatment surface so that the surgeon can adjust the distance betweenthe surface and the active electrodes.

In the embodiment shown in FIGS. 2-5, probe 20 includes a returnelectrode 112 for completing the current path between active electrodes104, loop electrode 103 and a high frequency power supply 10 (see FIG.1). As shown, return electrode 112 preferably comprises an annularexposed region of shaft 102 slightly proximal to tissue treatmentsurface 212 of electrode support member 102. Return electrode 112typically has a length of about 0.5 to 10 mm and more preferably about 1to 10 mm. Return electrode 112 is coupled to a connector that extends tothe proximal end of probe 10, where it is suitably connected to powersupply 10 (FIG. 1).

As shown in FIG. 2, return electrode 112 is not directly connected toactive electrodes 104 and loop electrode 103. To complete a current pathfrom active electrodes 104 or loop electrodes 103 to return electrode112, electrically conductive fluid (e.g., isotonic saline) is caused toflow therebetween. In the representative embodiment, the electricallyconductive fluid is delivered from a fluid delivery element (not shown)that is separate from probe 20. In arthroscopic surgery, for example,the joint cavity will be flooded with isotonic saline and the probe 20will be introduced into this flooded cavity. Electrically conductivefluid will be continually resupplied to maintain the conduction pathbetween return electrode 112 and active electrodes 104 and loopelectrode 103.

In alternative embodiments, the fluid path may be formed in probe 20 by,for example, an inner lumen or an annular gap (not shown) between thereturn electrode and a tubular support member within shaft 100. Thisannular gap may be formed near the perimeter of the shaft 100 such thatthe electrically conductive fluid tends to flow radially inward towardsthe target site, or it may be formed towards the center of shaft 100 sothat the fluid flows radially outward. In both of these embodiments, afluid source (e.g., a bag of fluid elevated above the surgical site orhaving a pumping device), is coupled to probe 20 via a fluid supply tube(not shown) that may or may not have a controllable valve. A morecomplete description of an electrosurgical probe incorporating one ormore fluid lumen(s) can be found in commonly assigned, co-pending patentapplication Ser. No. 08/485,219, filed on Jun. 7, 1995 (Attorney Docket16238-0006000), the complete disclosure of which is incorporated hereinby reference.

In addition, probe 20 may include an aspiration lumen (not shown) foraspirating excess conductive fluid, other fluids, such as blood, and/ortissue fragments from the target site. The probe may also include one ormore aspiration electrode(s), such as those described below in referenceto FIGS. 8-12, for ablating the aspirated tissue fragments.Alternatively, the aspiration electrode(s) may comprise the activeelectrodes described above. For example, the probe may have anaspiration lumen with a distal opening positioned adjacent one or moreof the active electrodes at the distal end of the probe. As tissuefragments are drawn into the aspiration lumen, the active electrodes areenergized to ablate at least a portion of these fragments to preventclogging of the lumen.

Referring now to FIG. 6, a surgical kit 300 for resecting and/orablating tissue within a joint according to the invention will now bedescribed. As shown, surgical kit 300 includes a package 302 for housinga surgical instrument 304, and an instructions for use 306 of instrument304. Package 302 may comprise any suitable package, such as a box,carton, wrapping, etc. In the exemplary embodiment, kit 300 furtherincludes a sterile wrapping 320 for packaging and storing instrument304. Instrument 304 includes a shaft 310 having at least one loopelectrode 311 and at least one active electrode 312 at its distal end,and at least one connector (not shown) extending from loop electrode 311and active electrode 312 to the proximal end of shaft 310. Theinstrument 304 is generally disposable after a single procedure.Instrument 304 may or may not include a return electrode 316.

The instructions for use 306 generally includes the steps of adjusting avoltage level of a high frequency power supply (not shown) to effectresection and/or ablation of tissue at the target site, connecting thesurgical instrument 304 to the high frequency power supply, positioningthe loop electrode 311 and the active electrode 312 within electricallyconductive fluid at or near the tissue at the target site, andactivating the power supply. The voltage level is usually about 40 to400 volts rms for operating frequencies of about 100 to 200 kHz. In apreferred embodiment, the positioning step includes introducing at leasta distal portion of the instrument 304 through a portal into a joint.

The present invention is particularly useful for lateral releaseprocedures, or for resecting and ablating a bucket-handle tear of themedial meniscus. In the latter technique, the probe is introducedthrough a medial port and the volume which surrounds the working end ofthe probe is filled with an electrically conductive fluid which may, byway of example, be isotonic saline or other biocompatible, electricallyconductive irrigant solution. When a voltage is applied between the loopelectrode and the return electrode, electrical current flows from theloop electrode, through the irrigant solution to the return electrode.The anterior horn is excised by pressing the exposed portion of the loopelectrode into the tear and removing one or more tissue fragments. Thedisplaced fragments are then ablated with the active electrodes asdescribed above.

Through a central patellar splitting approach, the probe is then placedwithin the joint through the intercondylar notch, and the attachedposterior horn insertion is resected by pressing the loop electrode intothe attached posterior fragment. The fragment is then removed with theactive electrodes and the remnant is checked for stability.

Referring now to FIG. 7, an exemplary electrosurgical system 411 fortreatment of tissue in ‘dry fields’ will now be described in detail. Ofcourse, system 411 may also be used in a ‘wet field’, i.e., the targetsite is immersed in electrically conductive fluid. However, this systemis particularly useful in ‘dry fields’ where the fluid is preferablydelivered through an electrosurgical probe to the target site. As shown,electrosurgical system 411 generally comprises an electrosurgicalhandpiece or probe 410 connected to a power supply 428 for providinghigh frequency voltage to a target site and a fluid source 421 forsupplying electrically conductive fluid 450 to probe 410. In addition,electrosurgical system 411 may include an endoscope (not shown) with afiber optic head light for viewing the surgical site, particularly insinus procedures or procedures in the ear or the back of the mouth. Theendoscope may be integral with probe 410, or it may be part of aseparate instrument. The system 411 may also include a vacuum source(not shown) for coupling to a suction lumen or tube (not shown) in theprobe 410 for aspirating the target site.

As shown, probe 410 generally includes a proximal handle 419 and anelongate shaft 418 having an array 412 of active electrodes 458 at itsdistal end. A connecting cable 434 has a connector 426 for electricallycoupling the active electrodes 458 to power supply 428. The activeelectrodes 458 are electrically isolated from each other and each of theterminals 458 is connected to an active or passive control networkwithin power supply 428 by means of a plurality of individuallyinsulated conductors (not shown). A fluid supply tube 415 is connectedto a fluid tube 414 of probe 410 for supplying electrically conductivefluid 450 to the target site.

Similar to the above embodiment, power supply 428 has an operatorcontrollable voltage level adjustment 430 to change the applied voltagelevel, which is observable at a voltage level display 432. Power supply428 also includes first, second and third foot pedals 437, 438, 439 anda cable 436 which is removably coupled to power supply 428. The footpedals 437, 438, 439 allow the surgeon to remotely adjust the energylevel applied to active electrodes 458. In an exemplary embodiment,first foot pedal 437 is used to place the power supply into the ablationmode and second foot pedal 438 places power supply 428 into the“coagulation” mode. The third foot pedal 439 allows the user to adjustthe voltage level within the “ablation” mode. In the ablation mode, asufficient voltage is applied to the active electrodes to establish therequisite conditions for molecular dissociation of the tissue (i.e.,vaporizing a portion of the electrically conductive fluid, ionizingcharged particles within the vapor layer, and accelerating these chargedparticles against the tissue). As discussed above, the requisite voltagelevel for ablation will vary depending on the number, size, shape andspacing of the electrodes, the distance to which the electrodes extendfrom the support member, etc. Once the surgeon places the power supplyin the ablation mode, voltage level adjustment 430 or third foot pedal439 may be used to adjust the voltage level to adjust the degree oraggressiveness of the ablation.

Of course, it will be recognized that the voltage and modality of thepower supply may be controlled by other input devices. However,applicant has found that foot pedals are convenient methods ofcontrolling the power supply while manipulating the probe during asurgical procedure.

In the coagulation mode, the power supply 428 applies a low enoughvoltage to the active electrodes (or the coagulation electrode) to avoidvaporization of the electrically conductive fluid and subsequentmolecular dissociation of the tissue. The surgeon may automaticallytoggle the power supply between the ablation and coagulation modes byalternately stepping on foot pedals 437, 438, respectively. This allowsthe surgeon to quickly move between coagulation and ablation in situ,without having to remove his/her concentration from the surgical fieldor without having to request an assistant to switch the power supply. Byway of example, as the surgeon is sculpting soft tissue in the ablationmode, the probe typically will simultaneously seal and/or coagulatesmall severed vessels within the tissue. However, larger vessels, orvessels with high fluid pressures (e.g., arterial vessels) may not besealed in the ablation mode. Accordingly, the surgeon can simply actuatefoot pedal 438, automatically lowering the voltage level below thethreshold level for ablation, and apply sufficient pressure onto thesevered vessel for a sufficient period of time to seal and/or coagulatethe vessel. After this is completed, the surgeon may quickly move backinto the ablation mode by actuating foot pedal 437. A specific design ofa suitable power supply for use with the present invention can be foundin Provisional Patent Application No. 60/062,997 filed Oct. 23, 1997(Attorney Docket No. 16238-007400), previously incorporated herein byreference.

FIGS. 8-10 illustrate an exemplary electrosurgical probe 490 constructedaccording to the principles of the present invention. As shown in FIG.8, probe 490 generally includes an elongated shaft 500 which may beflexible or rigid, a handle 604 coupled to the proximal end of shaft 500and an electrode support member 502 coupled to the distal end of shaft500. Shaft 500 preferably includes a bend 501 that allows the distalsection of shaft 500 to be offset from the proximal section and handle604. This offset facilitates procedures that require an endoscope, suchas FESS, because the endoscope can, for example, be introduced throughthe same nasal passage as the shaft 500 without interference betweenhandle 604 and the eyepiece of the endoscope (see FIG. 16). In oneembodiment, shaft 500 preferably comprises a plastic material that iseasily molded into a suitable shape.

In an alternative embodiment (not shown), shaft 500 comprises anelectrically conducting material, usually metal, which is selected fromthe group comprising tungsten, stainless steel alloys, platinum or itsalloys, titanium or its alloys, molybdenum or its alloys, and nickel orits alloys. In this embodiment, shaft 500 includes an electricallyinsulating jacket 508 which is typically formed as one or moreelectrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulating jacket over the shaft prevents direct electricalcontact between these metal elements and any adjacent body structure orthe surgeon. Such direct electrical contact between a body structure(e.g., tendon) and an exposed electrode could result in unwanted heatingand necrosis of the structure at the point of contact.

Handle 604 typically comprises a plastic material that is easily moldedinto a suitable shape for handling by the surgeon. Handle 604 defines aninner cavity (not shown) that houses the electrical connections 650(FIG. 10), and provides a suitable interface for connection to anelectrical connecting cable 422 (see FIG. 7). Electrode support member502 extends from the distal end of shaft 500 (usually about 1 to 20 mm),and provides support for a plurality of electrically isolated activeelectrodes 504 (see FIG. 9). As shown in FIG. 8, a fluid tube 633extends through an opening in handle 604, and includes a connector 635for connection to a fluid supply source, for supplying electricallyconductive fluid to the target site. Depending on the configuration ofthe distal surface of shaft 500, fluid tube 633 may extend through asingle lumen (not shown) in shaft 500, or it may be coupled to aplurality of lumens (also not shown) that extend through shaft 500 to aplurality of openings at its distal end. In the representativeembodiment, fluid tube 633 extends along the exterior of shaft 500 to apoint just proximal of return electrode 512 (see FIG. 9). In thisembodiment, the fluid is directed through an opening 637 past returnelectrode 512 to the active electrodes 504. Probe 490 may also include avalve 417 (FIG. 8) or equivalent structure for controlling the flow rateof the electrically conductive fluid to the target site.

As shown in FIG. 8, the distal portion of shaft 500 is preferably bentto improve access to the operative site of the tissue being treated.Electrode support member 502 has a substantially planar tissue treatmentsurface 612 that is usually at an angle of about 10 to 90 degreesrelative to the longitudinal axis of shaft 600, preferably about 30 to60 degrees and more preferably about 45 degrees. In alternativeembodiments, the distal portion of shaft 500 comprises a flexiblematerial which can be deflected relative to the longitudinal axis of theshaft. Such deflection may be selectively induced by mechanical tensionof a pull wire, for example, or by a shape memory wire that expands orcontracts by externally applied temperature changes. A more completedescription of this embodiment can be found in PCT InternationalApplication, U.S. National Phase Ser. No. PCT/US94/05168, filed on May10, 1994 (Attorney Docket 16238-000440), now U.S. Pat. No. 5,697,909,the complete disclosure of which has is incorporated herein byreference.

The bend in the distal portion of shaft 500 is particularly advantageousin the treatment of sinus tissue as it allows the surgeon to reach thetarget tissue within the nose as the shaft 500 extends through the nasalpassage. Of course, it will be recognized that the shaft may havedifferent angles depending on the procedure. For example, a shaft havinga 90° bend angle may be particularly useful for accessing tissue locatedin the back portion of the mouth and a shaft having a 10° to 30° bendangle may be useful for accessing tissue near or in the front portion ofthe mouth or nose

In the embodiment shown in FIGS. 8-10, probe 490 includes a returnelectrode 512 for completing the current path between active electrodes504 and a high frequency power supply (e.g., power supply 428, FIG. 8).As shown, return electrode 512 preferably comprises an annularconductive band coupled to the distal end of shaft 500 slightly proximalto tissue treatment surface 612 of electrode support member 502,typically about 0.5 to 10 mm and more preferably about 1 to 10 mm fromsupport member 502. Return electrode 512 is coupled to a connector 658that extends to the proximal end of probe 409, where it is suitablyconnected to power supply 428 (FIG. 7).

As shown in FIG. 8, return electrode 512 is not directly connected toactive electrodes 504. To complete this current path so that activeelectrodes 504 are electrically connected to return electrode 512,electrically conductive fluid (e.g., isotonic saline) is caused to flowtherebetween. In the representative embodiment, the electricallyconductive fluid is delivered through fluid tube 633 to opening 637, asdescribed above. Alternatively, the fluid may be delivered by a fluiddelivery element (not shown) that is separate from probe 490. Inarthroscopic surgery, for example, the joint cavity will be flooded withisotonic saline and the probe 490 will be introduced into this floodedcavity. Electrically conductive fluid will be continually resupplied tomaintain the conduction path between return electrode 512 and activeelectrodes 504.

In alternative embodiments, the fluid path may be formed in probe 490by, for example, an inner lumen or an annular gap between the returnelectrode and a tubular support member within shaft 500. This annulargap may be formed near the perimeter of the shaft 500 such that theelectrically conductive fluid tends to flow radially inward towards thetarget site, or it may be formed towards the center of shaft 500 so thatthe fluid flows radially outward. In both of these embodiments, a fluidsource (e.g., a bag of fluid elevated above the surgical site or havinga pumping device), is coupled to probe 490 via a fluid supply tube (notshown) that may or may not have a controllable valve. A more completedescription of an electrosurgical probe incorporating one or more fluidlumen(s) can be found in parent patent application Ser. No. 08/485,219,filed on Jun. 7, 1995 (Attorney Docket 16238-006000), the completedisclosure of is incorporated herein by reference.

Referring to FIG. 9, the electrically isolated active electrodes 504 arespaced apart over tissue treatment surface 612 of electrode supportmember 502. The tissue treatment surface and individual activeelectrodes 504 will usually have dimensions within the ranges set forthabove. As shown, the probe includes a single, larger opening 609 in thecenter of tissue treatment surface 612, and a plurality of activeelectrodes (e.g., about 3-15) around the perimeter of surface 612 (seeFIG. 9). Alternatively, the probe may include a single, annular, orpartially annular, active electrode at the perimeter of the tissuetreatment surface. The central opening 609 is coupled to a suction lumen(not shown) within shaft 500 and a suction tube 611 (FIG. 8) foraspirating tissue, fluids and/or gases from the target site. In thisembodiment, the electrically conductive fluid generally flows radiallyinward past active electrodes 504 and then back through the opening 609.Aspirating the electrically conductive fluid during surgery allows thesurgeon to see the target site, and it prevents the fluid from flowinginto the patient's body, e.g., through the sinus passages, down thepatient's throat or into the ear canal.

As shown, one or more of the active electrodes 504 comprise loopelectrodes 540 that extend across distal opening 609 of the suctionlumen within shaft 500. In the representative embodiment, two of theactive electrodes 504 comprise loop electrodes 540 that cross over thedistal opening 609. Of course, it will be recognized that a variety ofdifferent configurations are possible, such as a single loop electrode,or multiple loop electrodes having different configurations than shown.In addition, the electrodes may have shapes other than loops, such asthe coiled configurations shown in FIGS. 11 and 12. Alternatively, theelectrodes may be formed within the suction lumen proximal to the distalopening 609, as shown in FIG. 13. The main function of loop electrodes540 is to ablate portions of tissue that are drawn into the suctionlumen to prevent clogging of the lumen.

Loop electrodes 540 are electrically isolated from the other activeelectrodes 504, which can be referred to hereinafter as the ablationelectrodes 504. Loop electrodes 540 may or may not be electricallyisolated from each other. Loop electrodes 540 will usually extend onlyabout 0.05 to 4 mm, preferably about 0.1 to 1 mm from the tissuetreatment surface of electrode support member 504.

Of course, it will be recognized that the distal tip of the probe mayhave a variety of different configurations. For example, the probe mayinclude a plurality of openings 609 around the outer perimeter of tissuetreatment surface 612. In this embodiment, the active electrodes 504extend from the center of tissue treatment surface 612 radially inwardfrom openings 609. The openings are suitably coupled to fluid tube 633for delivering electrically conductive fluid to the target site, and asuction tube 611 for aspirating the fluid after it has completed theconductive path between the return electrode 512 and the activeelectrodes 504. In this embodiment, the ablation active electrodes 504are close enough to openings 609 to ablate most of the large tissuefragments that are drawn into these openings.

FIG. 10 illustrates the electrical connections 650 within handle 604 forcoupling active electrodes 504 and return electrode 512 to the powersupply 428. As shown, a plurality of wires 652 extend through shaft 500to couple terminals 504 to a plurality of pins 654, which are pluggedinto a connector block 656 for coupling to a connecting cable 422 (FIG.7). Similarly, return electrode 512 is coupled to connector block 656via a wire 658 and a plug 660.

In use, the distal portion of probe 490 is introduced to the target site(either endoscopically, through an open procedure, or directly onto thepatient's skin) and active electrodes 504 are positioned adjacent totissue at the target site. Electrically conductive fluid is deliveredthrough tube 633 and opening 637 to the tissue. The fluid flows past thereturn electrode 512 to the active electrodes 504 at the distal end ofthe shaft. The rate of fluid flow is controlled with valve 417 (FIG. 7)such that the zone between the tissue and electrode support 502 isconstantly immersed in the fluid. The power supply 428 is then turned onand adjusted such that a high frequency voltage difference is appliedbetween active electrodes 504 and return electrode 512. The electricallyconductive fluid provides the conduction path between active electrodes504 and the return electrode 512.

In the representative embodiment, the high frequency voltage issufficient to convert the electrically conductive fluid (not shown)between the target tissue and active electrodes 504 into an ionizedvapor layer or plasma (not shown). As a result of the applied voltagedifference between active electrode(s) 504 and the target tissue (i.e.,the voltage gradient across the plasma layer), charged particles in theplasma (e.g., electrons) are accelerated towards the tissue. Atsufficiently high voltage differences, these charged particles gainsufficient energy to cause dissociation of the molecular bonds withintissue structures. This molecular dissociation is accompanied by thevolumetric removal (i.e., ablative sublimation) of tissue and theproduction of low molecular weight gases, such as oxygen, nitrogen,carbon dioxide, hydrogen and methane. The short range of the acceleratedcharged particles within the tissue confines the molecular dissociationprocess to the surface layer to minimize damage and necrosis to theunderlying tissue.

During the process, the gases will be aspirated through opening 609 andsuction tube 611 to a vacuum source or collection reservoir (not shown).In addition, excess electrically conductive fluid and other fluids(e.g., blood) will be aspirated from the target site to facilitate thesurgeon's view. Applicant has also found that tissue fragments are alsoaspirated through opening 609 into suction lumen and tube 611 during theprocedure. These tissue fragments are ablated or dissociated with loopelectrodes 540 with a similar mechanism described above. Namely, aselectrically conductive fluid and tissue fragments are aspirated towardsloop electrodes 540, these electrodes are activated so that a highfrequency voltage is applied to loop electrodes 540 and return electrode512 (of course, the probe may include a different, separate returnelectrode for this purpose). The voltage is sufficient to vaporize thefluid, and create a plasma layer between loop electrodes 540 and thetissue fragments so that portions of the tissue fragments are ablated orremoved. This reduces the volume of the tissue fragments as they passthrough suction lumen to minimize clogging of the lumen.

In addition, the present invention is particularly useful for removingelastic tissue, such as the synovial tissue found in joints. Inarthroscopic procedures, this elastic synovial tissue tends to move awayfrom instruments within the conductive fluid, making it difficult forconventional instruments to remove this tissue. With the presentinvention, the probe is moved adjacent the target synovial tissue, andthe vacuum source is activated to draw the synovial tissue towards thedistal end of the probe. The aspiration and/or active electrodes arethen energized to ablate this tissue. This allows the surgeon to quicklyand precisely ablate elastic tissue with minimal thermal damage to thetreatment site.

In one embodiment, loop electrodes 540 are electrically isolated fromthe other active electrodes 504, and electrodes 540 must be separatelyactivated by power supply 428. In other embodiments, loop electrodes 540will be activated at the same time that active electrodes 504 areactivated. In this case, applicant has found that the plasma layertypically forms when tissue is drawn adjacent to loop electrodes 540.

Referring now to FIGS. 11 and 12, alternative embodiments for aspirationelectrodes will now be described. As shown in FIG. 11, the aspirationelectrodes may comprise a pair of coiled electrodes 550 that extendacross distal opening 609 of the suction lumen. The larger surface areaof the coiled electrodes 550 usually increases the effectiveness of theelectrodes 550 in ablating tissue fragments passing through opening 609.In FIG. 12, the aspiration electrode comprises a single coiled electrode552 passing across the distal opening 609 of suction lumen. This singleelectrode 552 may be sufficient to inhibit clogging of the suctionlumen. Alternatively, the aspiration electrodes may be positioned withinthe suction lumen proximal to the distal opening 609. Preferably, theseelectrodes are close to opening 609 so that tissue does not clog theopening 609 before it reaches electrode(s) 554. In this embodiment, aseparate return electrode 556 may be provided within the suction lumento confine the electric currents therein.

Referring to FIG. 13, another embodiment of the present inventionincorporates an aspiration electrode 560 within the aspiration lumen 562of the probe. As shown, the electrode 560 is positioned just proximal ofdistal opening 609 so that the tissue fragments are ablated as theyenter lumen 562. In the representative embodiment, the aspirationelectrode 560 comprises a loop electrode that extends across theaspiration lumen 562. However, it will be recognized that many otherconfigurations are possible. In this embodiment, the return electrode564 is located on the exterior of the probe, as in the previouslydescribed embodiments. Alternatively, the return electrode(s) may belocated within the aspiration lumen 562 with the aspiration electrode560. For example, the inner insulating coating 563 may be exposed atportions within the lumen 562 to provide a conductive path between thisexposed portion of return electrode 564 and the aspiration electrode560. The latter embodiment has the advantage of confining the electriccurrents to within the aspiration lumen. In addition, in dry fields inwhich the conductive fluid is delivered to the target site, it isusually easier to maintain a conductive fluid path between the activeand return electrodes in the latter embodiment because the conductivefluid is aspirated through the aspiration lumen 562 along with thetissue fragments.

FIGS. 14-17 illustrate a method for treating nasal or sinus blockages,e.g., chronic sinusitis, according to the present invention. In theseprocedures, the polyps, turbinates or other sinus tissue may be ablatedor reduced (e.g., by tissue contraction) to clear the blockage and/orenlarge the sinus cavity to reestablish normal sinus function. Forexample, in chronic rhinitis, which is a collective term for chronicirritation or inflammation of the nasal mucosa with hypertrophy of thenasal mucosa, the inferior turbinate may be reduced by ablation orcontraction. Alternatively, a turbinectomy or mucotomy may be performedby removing a strip of tissue from the lower edge of the inferiorturbinate to reduce the volume of the turbinate. For treating nasalpolypi, which comprises benign pedicled or sessile masses of nasal orsinus mucosa caused by inflammation, the nasal polypi may be contractedor shrunk, or ablated by the method of the present invention. Fortreating severe sinusitis, a frontal sinus operation may be performed tointroduce the electrosurgical probe to the site of blockage. The presentinvention may also be used to treat diseases of the septum, e.g.,ablating or resecting portions of the septum for removal, straighteningor reimplantation of the septum.

The present invention is particularly useful in functional endoscopicsinus surgery (FESS) in the treatment of sinus disease. In contrast toprior art microdebriders, the electrosurgical probe of the presentinvention effects hemostasis of severed blood vessels, and allows thesurgeon to precisely remove tissue with minimal or no damage tosurrounding tissue, bone, cartilage or nerves. By way of example and notlimitation, the present invention may be used for the followingprocedures: (1) uncinectomy or medial displacement or removal ofportions of the middle turbinate; (2) maxillary, sphenoid or ethmoidsinusotomies or enlargement of the natural ostium of the maxillary,sphenoid, or ethmoid sinuses, respectively; (3) frontal recessdissections, in which polypoid or granulation tissue are removed; (4)polypectomies, wherein polypoid tissue is removed in the case of severenasal polyposis; (5) concha bullosa resections or the thinning ofpolypoid middle turbinate; (6) septoplasty; and the like.

FIGS. 14-17 schematically illustrate an endoscopic sinus surgery (FESS)procedure according to the present invention. As shown in FIG. 14, anendoscope 700 is first introduced through one of the nasal passages 701to allow the surgeon to view the target site, e.g., the sinus cavities.As shown, the endoscope 700 will usually comprise a thin metal tube 702with a lens (not shown) at the distal end 704, and an eyepiece 706 atthe proximal end 708. As shown in FIG. 8, the probe shaft 500 has a bend501 to facilitate use of both the endoscope and the probe 490 in thesame nasal passage (i.e., the handles of the two instruments do notinterfere with each other in this embodiment). Alternatively, theendoscope may be introduced transorally through the inferior soft palateto view the nasopharynx. Suitable nasal endoscopes for use with thepresent invention are described in U.S. Pat. Nos. 4,517,962, 4,844,052,4,881,523 and 5,167,220, the complete disclosures of which areincorporated herein by reference for all purposes.

Alternatively, the endoscope 700 may include a sheath (not shown) havingan inner lumen for receiving the electrosurgical probe shaft 500. Inthis embodiment, the shaft 500 will extend through the inner lumen to adistal opening in the endoscope. The shaft will include suitableproximal controls for manipulation of its distal end during the surgicalprocedure.

As shown in FIG. 15, the distal end of probe 490 is introduced throughnasal passage 701 into the nasal cavity 703 (endoscope 700 is not shownin FIG. 15). Depending on the location of the blockage, the activeelectrodes 504 will be positioned adjacent the blockage in the nasalcavity 703, or in one of the paranasal sinuses 705, 707. Note that onlythe frontal sinus 705 and the sphenoidal sinus 707 are shown in FIG. 15,but the procedure is also applicable to the ethmoidal and maxillarysinuses. Once the surgeon has reached the point of major blockage,electrically conductive fluid is delivered through tube 633 and opening637 to the tissue (see FIG. 8). The fluid flows past the returnelectrode 512 to the active electrodes 504 at the distal end of theshaft. The rate of fluid flow is controlled by valve 417 (FIG. 8) suchthat the zone between the tissue and electrode support 502 is constantlyimmersed in the fluid. The power supply 428 is then turned on andadjusted such that a high frequency voltage difference is appliedbetween active electrodes 504 and return electrode 512. The electricallyconductive fluid provides the conduction path between active electrodes504 and the return electrode 512.

FIGS. 16A and 16B illustrate the removal of sinus tissue in more detailAs shown, the high frequency voltage is sufficient to convert theelectrically conductive fluid (not shown) between the target tissue 702and active electrode(s) 504 into an ionized vapor layer 712 or plasma.As a result of the applied voltage difference between activeelectrode(s) 504 (or active electrode 458) and the target tissue 702(i.e., the voltage gradient across the plasma layer 712), chargedparticles 715 in the plasma (e.g., electrons) are accelerated. Atsufficiently high voltage differences, these charged particles 715 gainsufficient energy to cause dissociation of the molecular bonds withintissue structures in contact with the plasma field. This moleculardissociation is accompanied by the volumetric removal (i.e., ablativesublimation) of tissue and the production of low molecular weight gases714, such as oxygen, nitrogen, carbon dioxide, hydrogen and methane. Theshort range of the accelerated charged particles 715 within the tissueconfines the molecular dissociation process to the surface layer tominimize damage and necrosis to the underlying tissue 720.

During the process, the gases 714 will be aspirated through opening 609and suction tube 611 to a vacuum source. In addition, excesselectrically conductive fluid, and other fluids (e.g., blood) will beaspirated from the target site 700 to facilitate the surgeon's view.During ablation of the tissue, the residual heat generated by thecurrent flux lines, will usually be sufficient to coagulate any severedblood vessels at the site. Typically, the temperature of the treatedtissue is less than 150° C. If the residual heat is not sufficient tocoagulate severed blood vessels, the surgeon may switch the power supply428 into the coagulation mode by lowering the voltage to a level belowthe threshold for fluid vaporization, as discussed above. Thissimultaneous hemostasis results in less bleeding and facilitates thesurgeon's ability to perform the procedure. Once the blockage has beenremoved, aeration and drainage are reestablished to allow the sinuses toheal and return to their normal function.

FIGS. 18-22 illustrate another embodiment of the present invention. Asshown in FIG. 18, an electrosurgical probe 800 includes an elongatedshaft 801 which may be flexible or rigid, a handle 804 coupled to theproximal end of shaft 801 and an electrode support member 802 coupled tothe distal end of shaft 801. As in previous embodiments, probe 800includes an active loop electrode 803 (e.g., FIG. 20) and a returnelectrode 812 (not shown), the latter spaced proximally from active loopelectrode 803. The probe 800 further includes a suction lumen 820 (FIG.19) for aspirating excess fluids, bubbles, tissue fragments, and/orproducts of ablation from the target site. As shown in FIGS. 19 and 22,suction lumen 820 extends through support member 802 to a distal opening822, and extends through shaft 801 and handle 804 to an externalconnector 824 for coupling to a vacuum source. Typically, the vacuumsource is a standard hospital pump that provides suction pressure toconnector 824 and lumen 820.

As shown in FIG. 19, handle 804 defines an inner cavity 808 that housesthe electrical connections 850 (discussed above), and provides asuitable interface for connection to an electrical connecting cable 22(see FIG. 1). As shown in FIG. 21, the probe will also include a codingresistor 860 having a value selected to program different output rangesand modes of operation for the power supply. This allows a single powersupply to be used with a variety of different probes in differentapplications (e.g., dermatology, cardiac surgery, neurosurgery,arthroscopy, etc).

Electrode support member 802 extends from the distal end of shaft 801(usually about 1 to 20 mm), and provides support for loop electrode 803and a ring electrode 804 (see FIG. 22). As shown in FIG. 20, loopelectrode 803 has first and second ends extending from the electrodesupport member 802. The first and second ends are each coupled to, orintegral with, one or more connectors, e.g., wires (not shown), thatextend through the shaft of the probe to its proximal end for couplingto the high frequency power supply. The loop electrode usually extendsabout 0.5 to about 10 mm from the distal end of support member,preferably about 1 to 2 mm. Loop electrode 803 usually extends furtheraway from the support member than the ring electrode 804 to facilitateablation of tissue. As discussed below, loop electrode 803 is especiallyconfigured for tissue ablation, while the ring electrode 804 ablatestissue fragments that are aspirated into suction lumen 820.

Referring to FIG. 22, ring electrode 804 preferably comprises a tungstenor titanium wire having two ends 830, 832 coupled to electricalconnectors (not shown) within support member 802. The wire is bent toform one-half of a figure eight, thereby forming a ring positioned overopening 822 of suction lumen 820. This ring inhibits passage of tissuefragments large enough to clog suction lumen 820. Moreover, voltagesapplied between ring electrode 804 and return electrode 812 providesufficient energy to ablate these tissue fragments into smallerfragments that are then aspirated through lumen 820. In a presentlypreferred embodiment, ring electrode 804 and loop electrode 803 areelectrically isolated from each other. However, electrodes 804, 803 maybe electrically coupled to each other in some applications.

FIGS. 25-31 illustrate another embodiment of the present inventionincluding an electrosurgical probe 900 incorporating an active screenelectrode 902. As shown in FIG. 25, probe 900 includes an elongatedshaft 904 which may be flexible or rigid, a handle 906 coupled to theproximal end of shaft 904 and an electrode support member 908 coupled tothe distal end of shaft 904. Probe 900 further includes an active screenelectrode 902 and a return electrode 910 spaced proximally from activescreen electrode 902. In this embodiment, active screen electrode 902and support member 908 are configured such that the active electrode 902is positioned on a lateral side of the shaft 904 (e.g., 90 degrees fromthe shaft axis) to allow the physician to access tissue that is offsetfrom the axis of the portal or arthroscopic opening into the jointcavity in which the shaft 904 passes during the procedure. To accomplishthis, probe 900 includes an electrically insulating cap 920 coupled tothe distal end of shaft 904 and having a lateral opening 922 forreceiving support member 908 and screen electrode 902.

The probe 900 further includes a suction connection tube 914 forcoupling to a source of vacuum, and an inner suction lumen 912 (FIG. 26)for aspirating excess fluids, tissue fragments, and/or products ofablation (e.g., bubbles) from the target site. In addition, suctionlumen 912 allows the surgeon to draw loose tissue, e.g., synovialtissue, towards the screen electrode 902, as discussed above. Typically,the vacuum source is a standard hospital pump that provides suctionpressure to connection tube 914 and lumen 912. However, a pump may alsobe incorporated into the high frequency power supply. As shown in FIGS.26, 27 and 30, internal suction lumen 912, which preferably comprisespeek tubing, extends from connection tube 914 in handle 906, throughshaft 904 to an axial opening 916 in support member 908, through supportmember 908 to a lateral opening 918. Lateral opening 918 contacts screenelectrode 902, which includes a plurality of holes 924 (FIG. 28) forallowing aspiration therethrough, as discussed below.

As shown in FIG. 26, handle 906 defines an inner cavity 926 that housesthe electrical connections 928 (discussed above), and provides asuitable interface for connection to an electrical connecting cable 22(see FIG. 1). As shown in FIG. 29, the probe will also include a codingresistor 930 having a value selected to program different output rangesand modes of operation for the power supply. This allows a single powersupply to be used with a variety of different probes in differentapplications (e.g., dermatology, cardiac surgery, neurosurgery,arthroscopy, etc).

Referring to FIG. 29, electrode support member 908 preferably comprisesan inorganic material, such as glass, ceramic, silicon nitride, aluminaor the like, that has been formed with lateral and axial openings 918,916 for suction, and with one or more smaller holes 930 for receivingelectrical connectors 932. In the representative embodiment, supportmember 908 has a cylindrical shape for supporting a circular screenelectrode 902. Of course, screen electrode 902 may have a variety ofdifferent shapes, such as the rectangular shape shown in FIG. 31, whichmay change the associated shape of support member 908. As shown in FIG.27, electrical connectors 932 extend from connections 928, through shaft904 and holes 930 in support member 908 to screen electrode 902 tocouple the active electrode 902 to a high frequency power supply. In therepresentative embodiment, screen electrode 902 is mounted to supportmember 908 by ball wires (not shown) that extend through holes 936 inscreen electrode 902 and holes 930 in support member 908. Ball wires 934function to electrically couple the screen 902 to connectors 932 and tosecure the screen 902 onto the support member 908. Of course, a varietyof other methods may be used to accomplish these functions, such asnailhead wires, adhesive and standard wires, a channel in the supportmember, etc.

The screen electrode 902 will comprise a conductive material, such astungsten, titanium, molybdenum, stainless steel, aluminum, gold, copperor the like. In some embodiments, it may be advantageous to constructthe active and return electrodes of the same material to eliminate thepossibility of DC currents being created by dissimilar metal electrodes.Screen electrode 902 will usually have a diameter in the range of about0.5 to 8 mm, preferably about 1 to 4 mm, and a thickness of about 0.05to about 2.5 mm, preferably about 0.1 to 1 mm. Electrode 902 willcomprise a plurality of holes 924 having sizes that may vary dependingon the particular application and the number of holes (usually from oneto 50 holes, and preferably about 3 to 20 holes). Holes 924 willtypically be large enough to allow ablated tissue fragments to passthrough into suction lumen 912, typically being about 2 to 30 mils indiameter, preferably about 5 to 20 mils in diameter. In someapplications, it may be desirable to only aspirate fluid and the gaseousproducts of ablation (e.g., bubbles) so that the holes may be muchsmaller, e.g., on the order of less than 10 mils, often less than 5mils.

In the representative embodiment, probe 900 is manufactured as follows:screen electrode 902 is placed on support member 908 so that holes 924are lined up with holes 930. One or more ball wires 934 are insertedthrough these holes, and a small amount of adhesive (e.g., epotek) isplaced around the outer face of support member 908. The ball wires 934are then pulled until screen 902 is flush with support member 908, andthe entire sub-assembly is cured in an oven or other suitable heatingmechanism. The electrode-support member sub-assembly is then insertedthrough the lateral opening in cap 920 and adhesive is applied to thepeek tubing suction lumen 912. The suction lumen 912 is then placedthrough axial hole 916 in support member 908 and this sub-assembly iscured. The return electrode 910 (which is typically the exposed portionof shaft 904) is then adhered to cap 920.

Another advantage of the present invention is the ability to preciselyablate layers of sinus tissue without causing necrosis or thermal damageto the underlying and surrounding tissues, nerves (e.g., the opticnerve) or bone. In addition, the voltage can be controlled so that theenergy directed to the target site is insufficient to ablate bone oradipose tissue (which generally has a higher impedance than the targetsinus tissue). In this manner, the surgeon can literally clean thetissue off the bone, without ablating or otherwise effecting significantdamage to the bone.

Methods for treating air passage disorders according to the presentinvention will now be described. In these embodiments, anelectrosurgical probe such as one described above can be used to ablatetargeted masses including, but not limited to, the tongue, tonsils,turbinates, soft palate tissues (e.g., the uvula), hard tissue andmucosal tissue. In one embodiment, selected portions of the tongue 714are removed to treat sleep apnea. In this method, the distal end of anelectrosurgical probe 490 is introduced into the patient's mouth 710, asshown in FIG. 17. An endoscope (not shown), or other type of viewingdevice, may also be introduced, or partially introduced, into the mouth710 to allow the surgeon to view the procedure (the viewing device maybe integral with, or separate from, the electrosurgical probe). Theactive electrodes 504 are positioned adjacent to or against the backsurface 716 of the tongue 714, and electrically conductive fluid isdelivered to the target site, as described above. The power supply 428is then activated to remove selected portions of the back of the tongue714, as described above, without damaging sensitive structures, such asnerves, and the bottom portion of the tongue 714.

In another embodiment, the electrosurgical probe of the presentinvention can be used to ablate and/or contract soft palate tissue totreat snoring disorders. In particular, the probe is used to ablate orshrink sections of the uvula 720 without causing unwanted tissue damageunder and around the selected sections of tissue. For tissuecontraction, a sufficient voltage difference is applied between theactive electrodes 504 and the return electrode 512 to elevate the uvulatissue temperature from normal body temperatures (e.g., 37° C.) totemperatures in the range of 45° C. to 90° C., preferably in the rangefrom 60° C. to 70° C. This temperature elevation causes contraction ofthe collagen connective fibers within the uvula tissue.

In addition to the above procedures, the system and method of thepresent invention may be used for treating a variety of disorders in themouth 710, pharynx 730, larynx 735, hypopharynx, trachea 740, esophagus750 and the neck 760. For example, tonsillar hyperplasia or other tonsildisorders may be treated with a tonsillectomy by partially ablating thelymphoepithelial tissue. This procedure is usually carried out underintubation anesthesia with the head extended. An incision is made in theanterior faucial pillar, and the connective tissue layer between thetonsillar parenchyma and the pharyngeal constrictor muscles isdemonstrated. The incision may be made with conventional scalpels, orwith the electrosurgical probe of the present invention. The tonsil isthen freed by ablating through the upper pole to the base of the tongue,preserving the faucial pillars. The probe ablates the tissue, whileproviding simultaneous hemostasis of severed blood vessels in theregion. Similarly, adenoid hyperplasia, or nasal obstruction leading tomouth breathing difficulty, can be treated in an adenoidectomy byseparating (e.g., resecting or ablating) the adenoid from the base ofthe nasopharynx.

Other pharyngeal disorders can be treated according to the presentinvention. For example, hypopharyngeal diverticulum involves smallpouches that form within the esophagus immediately above the esophagealopening. The sac of the pouch may be removed endoscopically according tothe present invention by introducing a rigid esophagoscope, andisolating the sac of the pouch. The cricopharyngeus muscle is thendivided, and the pouch is ablated according to the present invention.Tumors within the mouth and pharynx, such as hemangiomas, lymphangiomas,papillomas, lingual thyroid tumors, or malignant tumors, may also beremoved according to the present invention.

Other procedures of the present invention include removal of vocal cordpolyps and lesions and partial or total laryngectomies. In the latterprocedure, the entire larynx is removed from the base of the tongue tothe trachea, if necessary with removal of parts of the tongue, thepharynx, the trachea and the thyroid gland.

Tracheal stenosis may also be treated according to the presentinvention. Acute and chronic stenoses within the wall of the trachea maycause coughing, cyanosis and choking.

FIG. 23 schematically illustrates a lipectomy procedure in the abdomenaccording to the present invention. In a conventional liposuctionprocedure according to the prior art, multiple incisions are made toallow cross-tunneling, and the surgeon will manipulate the suctioncannula in a linear piston-like motion during suction to remove theadipose tissue to avoid clogging of the cannula, and to facilitateseparation of the fatty tissue from the remaining tissue. The presentinvention mostly solves these two problems and, therefore, minimizes theneed for the surgeon to manipulate the probe in such a fashion.

Liposuction in the abdomen, lower torso and thighs according to thepresent invention removes the subcutaneous fat in these regions whileleaving the fascial, neurovascular and lymphatic network intact or onlymildly compromised. As shown, access incisions 1200 are typicallypositioned in natural skin creases remote from the areas to beliposuctioned. As shown in FIG. 23, the distal portion (not shown) of anelectrosurgical instrument is introduced through one or more of theincisions 1200 and one or more active electrode(s) are positionedadjacent the fatty tissue. Electrically conductive fluid, e.g., isotonicsaline, is delivered through tube 1133 and opening 1137 to the tissue.The fluid flows past the return electrode to the active electrodes atthe distal end of the shaft. The rate of fluid flow is controlled by avalve 417 (FIG. 7) such that the zone between the tissue and electrodesupport 1002 is constantly immersed in the fluid. The power supply 928is then turned on and adjusted such that a high frequency voltagedifference is applied between active electrodes 1004 and returnelectrode 1012. The electrically conductive fluid provides theconduction path between active electrodes 1004 and the return electrode1012.

In the representative embodiment, the high frequency voltage issufficient to convert the electrically conductive fluid (not shown)between the target tissue and active electrodes 1004 into an ionizedvapor layer or plasma (not shown). As a result of the applied voltagedifference between active electrode(s) 1004 and the target tissue (i.e.,the voltage gradient across the plasma layer), charged particles in theplasma (e.g., electrons) are accelerated towards the fatty tissue. Atsufficiently high voltage differences, these charged particles gainsufficient energy to cause dissociation of the molecular bonds withintissue structures. This molecular dissociation is accompanied by thevolumetric removal (i.e., ablative sublimation) of tissue and theproduction of low molecular weight gases, such as oxygen, nitrogen,carbon dioxide, hydrogen and methane. The short range of the acceleratedcharged particles within the tissue confines the molecular dissociationprocess to the surface layer to minimize damage and necrosis to theunderlying tissue.

In alternative embodiments, the high frequency voltage is sufficient toheat and soften or separate portions of the fatty tissue from thesurrounding tissue. Suction is then applied from a vacuum source (notshown) through lumen 962 to aspirate or draw away the heated fattytissue. A temperature of about 45° C. softens fatty tissue, and atemperature of about 50° C. normally liquefies mammalian adipose tissue.This heating and softening of the fatty tissue reduces the collateraldamage created when the heated tissue is then removed throughaspiration. Alternatively, the present invention may employ acombination of ablation through molecular dissociation, as describedabove, and heating or softening of the fatty tissue. In this embodiment,some of the fatty tissue is ablated in situ, while other portions aresoftened to facilitate removal through suction.

During the process, the gases will be aspirated through opening 1109 andsuction tube 1111 to a vacuum source. In addition, excess electricallyconductive fluid, and other fluids (e.g., blood) will be aspirated fromthe target site to facilitate the surgeon's view. Applicant has alsofound that tissue fragments are also aspirated through opening 1109 intosuction lumen and tube 1111 during the procedure. These tissue fragmentsare ablated or dissociated with loop electrodes 1040 in a similarmechanism to that described above. That is, as electrically conductivefluid and tissue fragments are aspirated towards loop electrodes 1040,these electrodes 1040 are activated so that a high frequency voltage isapplied between loop electrodes 1040 and return electrode 1012 (ofcourse, the probe may include a different, separate return electrode forthis purpose). The voltage is sufficient to vaporize the fluid, andcreate a plasma layer between loop electrodes 1040 and the tissuefragments so that portions of the tissue fragments are ablated orremoved. This reduces the volume of the tissue fragments as they passthrough suction lumen to minimize clogging of the lumen.

In one embodiment, loop electrodes 1040 are electrically isolated fromthe other active electrodes 1004, and electrodes 1040 must be separatelyactivated at the power supply 928. In other embodiments, loop electrodes1040 will be activated at the same time that active electrodes 1004 areactivated. In this case, applicant has found that the plasma layertypically forms when tissue is drawn adjacent to loop electrodes 1040.

FIG. 24 illustrates a cervical liposuction procedure in the face andneck according to the present invention. As shown, the distal portion ofthe electrosurgical probe 1202 may be inserted in either submental orretroauricular incisions 1204 in the face and neck. In this procedure,the probe 1202 is preferably passed through a portion of the fattytissue with the power supply 928 activated, but without suction toestablish a plane of dissection at the most superficial level of desiredfat removal. This plane of dissection allows a smooth, supple, redrapingof the region after liposuction has been completed. If this“pretunneling” is not performed in this region, the cannula has atendency to pull the skin inward, creating small pockets andindentations in the skin, which become evident as superficialirregularities after healing. Pretunneling also enables accurate, safeand proper removal of fat deposits while preserving a fine cushion ofsubdermal fat.

The present invention may also be used to perform lipectomies incombination with face and neck lifts to facilitate the latterprocedures. After the cervical liposuction is complete, the skin flapsare elevated in the temporal, cheek and lateral regions. The lateralneck skin flap dissection is greatly facilitated by the previous suctionlipectomy in that region, and the medial and central skin flap elevationmay be virtually eliminated.

In another embodiment, the present invention comprises an electrifiedshaver or microdebrider. Powered instrumentation, such as microdebriderdevices and shavers, has been used to remove polyps or other swollentissue in functional endoscopic sinus surgery and synovial and meniscustissue and articular cartilage I arthroscopic procedures. These poweredinstruments are disposable motorized cutters having a rotating shaftwith a serrated distal tip for cutting and resecting tissue. The handleof the microdebrider is typically hollow, and it accommodates a smallvacuum, which serves to aspirate debris. In this procedure, the distaltip of the shaft is endoscopically delivered to a target site of thepatient's body, and an external motor rotates the shaft and the serratedtip, allowing the tip to cut tissue, which is then aspirated through theinstrument.

While microdebriders and shavers of the prior art have shown somepromise, these devices suffer from a number of disadvantages. For onething, these devices sever blood vessels within the tissue, usuallycausing profuse bleeding that obstructs the surgeon's view of the targetsite. Controlling this bleeding can be difficult since the vacuumingaction tends to promote hemorrhaging from blood vessels disrupted duringthe procedure. In addition, usually the microdebrider or shaver of theprior art must be periodically removed from the patient to cauterizesevered blood vessels, thereby lengthening the procedure. Moreover, theserrated edges and other fine crevices of the microdebrider and shavercan easily become clogged with debris, which requires the surgeon toremove and clean the microdebrider during the surgery, furtherincreasing the length of the procedure.

The present invention solves the above problems by providing one or moreactive electrodes at the distal tip of the aspiration instrument toeffect hemostasis of severed blood vessels at the target site. Thisminimizes bleeding to clear the surgical site, and to reducepostoperative swelling and pain. In addition, by providing an aspirationelectrode on or near the suction lumen, as described above, the presentinvention avoids the problems of clogging inherent with these devices.

The systems of the present invention may include a bipolar arrangementof electrodes designed to ablate tissue at the target site, and thenaspirate tissue fragments, as described above. Alternatively, theinstrument may also include a rotating shaft with a cutting tip forcutting tissue in a conventional manner. In this embodiment, theelectrode(s) serve to effect hemostasis at the target site and to reduceclogging of the aspiration lumen, while the rotating shaft and cuttingtip do the bulk of tissue removal by cutting the tissue in aconventional manner.

The system and method of the present invention may also be useful toefficaciously ablate (i.e., disintegrate) cancer cells and tissuecontaining cancer cells, such as cancer on the surface of the epidermis,eye, colon, bladder, cervix, uterus and the like. The presentinvention's ability to completely disintegrate the target tissue can beadvantageous in this application because simply vaporizing andfragmenting cancerous tissue may lead to spreading of viable cancercells (i.e., seeding) to other portions of the patient's body or to thesurgical team in close proximity to the target tissue. In addition, thecancerous tissue can be removed to a precise depth while minimizingnecrosis of the underlying tissue.

In another aspect of the invention, systems and methods are provided fortreating articular cartilage defects, such as chondral fractures orchondromalicia. The method comprises positioning a distal end of anelectrosurgical instrument, such as a probe or a catheter, into closeproximity to an articular cartilage surface, either arthroscopically orthrough an open procedure. High frequency voltage is then appliedbetween an active electrode on the instrument and a return electrodesuch that electric current flows therebetween and sufficient energy isimparted to the articular cartilage to smooth its surface or to reduce alevel of fibrillation in the cartilage. In treating chondromalicia, thevoltage between the electrodes is sufficient to heat (e.g., shrink) orablate (i.e., remove) cartilage strands extending from the articularcartilage surface. In treating chondral fractures, lesions or otherdefects, the voltage is typically sufficient to ablate or heat at leasta portion of the diseased tissue while leaving behind a smooth,contoured surface. In both cases, the method preferably includes forminga substantially continuous matrix layer on the surface of the tissue toseal the tissue, insulating the fracturing and fissuring within thearticular cartilage that can cause further degeneration.

The present invention provides a highly controlled application of energyacross the articular cartilage, confining the effect to the surface toproduce precise and anatomically optimal tissue sculpting thatstabilizes the articular cartilage and minimizes collateral tissueinjury. Results to date demonstrate that cultures of post-treatedchondrocytes within the cartilage tissue remain viable for at least onemonth, confirming that remaining chrondrocytes remain viable after thisprocedure. Moreover, minimal to no collagen abnormalities have beendetected in post-operative cartilage tissue, and diseased areas aresmoothed without further evidence of fibrillation. In addition, thebipolar configuration of the present invention controls the flow ofcurrent to the immediate region around the distal end of the probe,which minimizes tissue necrosis and the conduction of current throughthe patient. The residual heat from the electrical energy also providessimultaneous hemostasis of severed blood vessels, which increasesvisualization of the surgical field for the surgeon, and improvesrecovery time for the patient. The techniques of the present inventionproduce significantly less thermal energy than many conventionaltechniques, such as lasers and conventional RF devices, which reducescollateral tissue damage and minimizes pain and postoperative scarring.Patients generally experience less pain and swelling, and consequentlyachieve their range of motion earlier. A more complete description ofexemplary systems and methods for treating articular cartilage can befound in co-pending commonly assigned U.S. patent application Ser. Nos.09/183,838, filed Oct. 30, 1998 and 09/177,861, filed Oct. 23, 1998,(Attorney Docket Nos. A-13 and A-2-4, respectively), the completedisclosures of which are incorporated herein by reference.

In another aspect, the present invention provides an electrosurgicalprobe having at least one active loop electrode for resecting andablating tissue. In comparison to the planar electrodes, ballelectrodes, or the like, the active loop electrodes provide a greatercurrent concentration to the tissue at the target site. The greatercurrent concentration can be used to aggressively create a plasma withinthe electrically conductive fluid, and hence a more efficient resectionof the tissue at the target site. In use, the loop electrode(s) aretypically employed to ablate tissue using the Coblation® mechanisms asdescribed above. Voltage is applied between the active loop electrodesand a return electrode to volumetrically loosen fragments from thetarget site through molecular dissociation. Once the tissue fragmentsare loosened from the target site, the tissue fragments can be ablatedin situ within the plasma (i.e., break down the tissue by processesincluding molecular dissociation or disintegration).

In some embodiments, the loop electrode(s) provide a relatively uniformsmooth cutting or ablation effect across the tissue. The loop electrodesgenerally have a larger surface area exposed to electrically conductivefluid (as compared to the smaller active electrodes described above),which increases the rate of ablation of tissue.

Applicants have found that the current concentrating effects of the loopelectrodes further provide reduced current dissipation into thesurrounding tissue, and consequently improved patient comfort throughthe reduced stimulation of surrounding nerves and muscle. Preferably,the loop electrode(s) extend a sufficient distance from the electrodesupport member to achieve current concentration and an improved ablationrate while simultaneously reducing current dissipation into thesurrounding medium (which can cause undesirable muscle stimulation,nerve stimulation, or thermal damage to surrounding or underlyingtissue). In an exemplary embodiment, the loop electrode has a lengthfrom one end to the other end of about 0.5 mm to 20 mm, usually about 1mm to 8 mm. The loop electrode usually extends about 0.25 mm to 10 mmfrom the distal end of the support member, preferably about 1 mm to 4mm.

The loop electrode(s) may have a variety of cross-sectional shapes.Electrode shapes according to the present invention can include the useof formed wire (e.g., by drawing round wire through a shaping die) toform electrodes with a variety of cross-sectional shapes, such assquare, rectangular, L or V shaped, or the like. Electrode edges mayalso be created by removing a portion of the elongate metal electrode toreshape the cross-section. For example, material can be removed alongthe length of a solid or hollow wire electrode to form D or C shapedwires, respectively, with edges facing in the cutting direction.Alternatively, material can be removed at closely spaced intervals alongthe electrode length to form transverse grooves, slots, threads or thelike along the electrodes.

In yet another aspect, the present invention provides an electrosurgicalprobe having an aspiration lumen with an opening that is spacedproximally from the active electrodes. Applicants have found that byspacing the suction lumen opening proximal of the active electrodes thata more aggressive plasma can be created. In use, the saline is deliveredto the target site and allowed to remain in contact with the electrodesand tissue for a longer period of time. By increasing the distancebetween the aspiration lumen and the conductive fluid, the dwell time ofthe conductive fluid is increased and the plasma can be aggressivelycreated. Advantageously, by moving the aspiration lumen out of thetarget area, the suction will primarily aspirate blood and gas bubblesfrom the target site, while leaving the conductive fluid in the targetarea. Consequently, less conductive fluid and tissue fragments areaspirated from the target site and less clogging of the aspiration lumenoccurs.

In a further aspect, the present invent provides an electrosurgicalprobe having a conductive fluid delivery lumen that has at least onedistal opening positioned at least partially around the activeelectrodes. The configuration of the openings can be completely aroundthe active electrodes (e.g., O configuration or annular shaped) orpartially around the active electrodes (e.g., U configuration or Cconfiguration) such that delivery of the conductive fluid immerses theactive electrodes with conductive fluid during the ablation or resectionprocedure. Because the conductive fluid can be delivered from aplurality of directions, the dwell time of the conductive fluid isincreased, and consequently the creation of the plasma can be improved.

In a preferred embodiment, the conductive fluid lumen comprises aplurality of openings that are positioned so as to substantiallysurround the active electrode array. As above, by “substantiallysurround”, is meant that the openings are at least partially around theactive electrodes. In some configurations, the openings will be equallyspaced around the active electrodes. However, it will be appreciatedthat in other alternative embodiments, the openings will only partiallysurround the active electrodes or can be unevenly spaced about theactive electrodes.

With reference to FIGS. 32-45 there follows a description of anelectrosurgical probe 1400 including a resection unit 1406, according tovarious embodiments of the instant invention. Probe 1400 is adapted foraggressive ablation, for resection, or for combined ablation andresection of tissue. Probe 1400 may be used in a broad range of surgicalprocedures including, without limitation, those listed or describedhereinabove with reference to the apparatus of FIGS. 1-31. In someembodiments, resection unit 1406 may be used to resect tissue bymechanical abrasion, cutting, or severing of tissue. In someembodiments, resection unit 1406 may be used to ablate tissue, e.g., viaa Coblation® (cool ablation) mechanism. The Coblation® mechanism hasbeen described hereinabove. Briefly, and without being bound by theory,Coblation® involves the localized generation of a plasma by theapplication of a high frequency voltage between at least one activeelectrode and a return electrode in the presence of an electricallyconductive fluid. The plasma thus generated causes the breakdown oftissues, e.g., via molecular dissociation, to form low molecular weightablation by-products. Such low molecular weight ablation by-products maybe easily removed from a target site, e.g., via aspiration. Coblation®allows the controlled removal of tissue, in which both the quantity andquality of tissue removed can be accurately determined. In someembodiments, resection unit 1406 may be used for combined resection andablation: to resect tissue by application of a mechanical force to thetissue and, concurrently therewith, to electrically ablate (“Coblate”)the tissue contacted by resection unit 1406. Applicants have found thata combination of mechanical resection and electrical ablation byresection unit 1406 provides advantageous tissue removal, as comparedwith mechanical resection or electrical ablation alone. Advantages oftissue removal by combined resection and ablation by resection unit 1406include a more rapid and aggressive tissue removal, as compared withablation alone; and a more controlled and less traumatic tissue removal,as compared with mechanical resection alone.

FIG. 32 shows probe 1400 including a shaft 1402 affixed at shaftproximal end portion 1402 b to a handle 1404. Resection unit 1406 isdisposed on shaft distal end portion 1402 a. Although FIG. 32 shows onlya single resection unit 1406 on shaft 1402, certain embodiments of theinstant invention may include a plurality of resection units 1406 whichmay be alike or dissimilar in various respects (for example, the sizeand shape of electrode support 1408, and the number, arrangement, andtype of resection electrodes 1410) (FIG. 33). In the embodiment of FIG.32, a return electrode 1420 is located at shaft distal end portion 1402a. Return electrode 1420 may be in the form of an annular band.Resection unit 1406 is shown in FIG. 32 as being arranged within, orsurrounded by, return electrode 1420. In other embodiments, resectionunit 1406 may be arranged adjacent to return electrode 1420. Under theinvention, shaft 1402 may be provided in a range of different lengthsand diameters. Preferably, shaft 1402 has a length in the range of fromabout 5 cm to about 30 cm; more preferably in the range of from about 10cm to about 25 cm. Preferably, shaft 1402 has a diameter in the range offrom about 1 mm to about 20 mm; more preferably in the range of fromabout 2 mm to about 10 mm.

FIG. 33 schematically represents resection unit 1406 of probe 1400,wherein resection unit 1406 includes a resection electrode 1410 on aresection electrode support member 1408. In FIG. 33 resection electrode1410 is represented as a single “box” located within support 1408,however, other arrangements and numbers of resection electrode 1410 arecontemplated and are within the scope of the invention (see, forexample, FIGS. 36A-F, FIGS. 41A-C). Resection electrode support 1408 maycomprise an electrically insulating, and durable or refractory material,such as a glass, a ceramic, a silicone, a polyurethane, a urethane, apolyimide, silicon nitride, teflon, or alumina, and the like. Resectionelectrode support 1408 is shown in FIG. 33 as being substantially squarein outline, however, a broad range of other shapes are also possible.The size of resection electrode support 1408 may depend on a number offactors, including the diameter or width of shaft 1402. In oneembodiment, support 1408 may be mounted laterally on shaft 1402 as anannular band, i.e., support 1408 may completely encircle shaft 1402.Typically support 1408 represents or occupies from about 2% to 100% ofthe circumference of shaft 1402. More typically, support 1408 occupiesfrom about 50% to 80% of the circumference of shaft 1402, most typicallyfrom about 10% to 50% of the circumference of shaft 1402. In embodimentswherein support 1408 is mounted terminally on shaft 1402, support 1408typically occupies from about 5% to 100% of the cross-sectional area ofshaft 1402, more typically from about 10% to 95% of the cross-sectionalarea of shaft 1402.

FIGS. 34A-D each show an electrosurgical probe 1400, according tocertain embodiments of the invention. Probe 1400 is depicted in FIGS.34A-D as being linear, however, according to various embodiments of theinvention, shaft 1402 may include one or more curves or bends therein(see, for example, FIG. 43B). Resection electrodes 1410 are omitted fromFIGS. 34A-D for the sake of clarity. However, as described elsewhereherein, each resection unit 1406 includes at least one resectionelectrode 1410 (see, for example, FIGS. 36A-F, 38A-D, 41A-C).

With reference to FIG. 34A, probe 1400 includes a fluid delivery tube1434, and a fluid delivery port 1430 located distal to resection unit1406 on shaft distal end portion 1402 a. Fluid delivery port 1430 iscoupled to fluid delivery tube 1434 via a fluid delivery lumen 1432(FIG. 35B). Fluid delivery tube 1434 is, in turn, coupled to a source ofan electrically conductive fluid (see, e.g., FIG. 7). Fluid deliveryport 1430 is adapted to provide a quantity of an electrically conductivefluid to shaft distal end portion 1402 a during a procedure, as isdescribed elsewhere herein in enabling detail.

FIG. 34B shows probe 1400 including an aspiration tube 1444 and anaspiration port 1440 located proximal to resection unit 1406. In theembodiment depicted in FIG. 34B, aspiration tube 1444 is shown as beingconnected to probe 1400 at shaft proximal end 1402 b, however otherarrangements for coupling aspiration tube 1444 to probe 1400 arepossible under the invention. FIG. 34C shows probe 1400 including bothan aspiration tube 1444 and a fluid delivery tube 1434; and both a fluiddelivery port 1430 and an aspiration port 1440. Although fluid deliveryport 1430 is depicted in FIGS. 34A, 34C as a single port located distalto resection unit 1406, other arrangements of fluid delivery port(s)1430/1430′ with respect to resection unit 1406, are contemplatedaccording to various embodiments of the invention. Aspiration port 1440is located proximal to resection unit 1406. Preferably, aspiration port1440 is located a distance of at least 2 mm proximal to resection unit1406. More preferably, aspiration port 1440 is located a distance in therange of from about 4 mm to about 50 mm proximal to resection unit 1406.In one embodiment, aspiration port 1440 may have a screen (not shown) toprevent relatively large fragments of resected tissue from enteringaspiration lumen 1442 (FIG. 35A). Such a screen may serve as an activeelectrode and cause ablation of tissue fragments which contact thescreen. Alternatively, the screen may serve as a mechanical sieve orfilter to exclude entry of relatively large tissue fragments into lumen1442.

FIG. 34D shows probe 1400 in which resection unit 1406 is located at thedistal terminus of shaft 1402. In this embodiment, return electrode 1420is located at shaft distal end 1402 a, and aspiration port 1440 islocated proximal to return electrode 1420. The embodiment of FIG. 34Dmay further include one or more fluid delivery ports 1430 (see, forexample, FIGS. 44A-D) for delivering an electrically conductive fluidto, at least, resection unit 1406. In certain embodiments, fluiddelivery port(s) 1430 deliver a quantity of an electrically conductivefluid to shaft distal end 1402 a sufficient to immerse resection unit1406 and return electrode 1420. In some embodiments, fluid deliveryport(s) 1430 deliver a quantity of an electrically conductive fluid fromshaft distal end 1402 a sufficient to immerse the tissue at a sitetargeted for ablation and/or resection.

FIG. 35A shows electrosurgical probe 1400 including resection unit 1406and aspiration port 1440 proximal to resection unit 1406, according toone embodiment of the invention. Aspiration port 1440 is coupled toaspiration tube 1444 via an aspiration lumen 1442. Aspiration tube 1444may be coupled to a vacuum source, as is well known in the art.Aspiration lumen 1442 serves as a conduit for removal of unwantedmaterials (e.g., excess fluids and resected tissue fragments) from thesurgical field or target site of an ablation and/or resection procedure,essentially as described hereinabove with reference to other embodimentsof an electrosurgical probe. The embodiment of FIG. 35A may furtherinclude a fluid delivery device (see, for example, FIG. 35B).

FIG. 35B shows electrosurgical probe 1400 including resection unit 1406and fluid delivery port 1430 located distal to resection unit 1406,according to one embodiment of the invention. Fluid delivery port 1430is coupled to fluid delivery tube 1434 via a fluid delivery lumen 1432.Fluid delivery lumen 1432 serves as a conduit for providing a quantityof an electrically conductive fluid to resection unit 1406 and/or thetarget site of an ablation and resection procedure. The embodiment ofFIG. 35B may further include an aspiration device (see, for example,FIG. 35A). In the embodiment of FIG. 35B, tube 1434 is coupled to probe1400 at handle 1404, however other arrangements for coupling tube 1434to probe 1400 are also within the scope of the invention.

FIGS. 36A-F each show a resection unit 1406 a-f as seen in plan view,wherein each resection unit 1406 a-f includes a resection electrodesupport 1408 and at least one resection electrode head 1412, accordingto various embodiments of the invention. Each resection electrode 1410(e.g., FIG. 33), may have a single terminal or resection electrode head1412, such that each resection electrode head 1412 is independentlycoupled to a power supply (e.g., power supply 428 of FIG. 7).Alternatively, each resection electrode 1410 may have a plurality ofterminals or resection electrode heads 1412. Each resection electrode1410 may be coupled to a power supply unit (not shown in FIGS. 36A-F)via a connection block and connector cable, essentially as describedhereinabove (e.g., with reference to FIGS. 7 & 10).

FIG. 36A indicates the longitudinal axis 1406′ of resection units 1406a-f, as well as electrode support distal end 1408 a (indication oflongitudinal axis 1406′ and support distal end 1408 a are omitted fromFIGS. 36B-F for the sake of clarity, however the orientation ofresection units 1406 b-f is the same as that of resection unit 1406 a).In each of FIGS. 36A-F, resection electrode heads 1412 are depicted ashaving an elongated, substantially rectangular shape in plan view.However, other shapes and arrangements for resection electrode heads1412 are also within the scope of the invention.

FIGS. 36A-F show just some of the arrangements of resection electrodehead(s) 1412 on each resection electrode support 1408, according tovarious embodiments. Briefly, FIG. 36A shows a single resectionelectrode head 1412 located substantially centrally within support 1408and aligned approximately perpendicular to longitudinal axis 1406′. FIG.36B shows a plurality of resection electrode heads 1412 arrangedsubstantially parallel to each other and aligned substantiallyperpendicular to axis 1406′. FIG. 36C shows a plurality of resectionelectrode heads 1412 arranged substantially parallel to each other andaligned substantially perpendicular to axis 1406′, and an additionalresection electrode head 1412 arranged substantially parallel to axis1406′. FIG. 36D shows a plurality of resection electrode heads 1412arranged substantially parallel to each other and aligned at an angleintermediate between parallel to axis 1406′ and perpendicular to axis1406′. FIG. 36E shows a plurality of resection electrode heads 1412including a first substantially parallel array 1412 a aligned at a firstangle with respect to axis 1406′ and a second substantially parallelarray 1412 b aligned at a second angle with respect to axis 1406′. FIG.36F shows a plurality of resection electrode heads 1412 having anarrangement similar to that described for FIG. 36E, wherein resectionelectrode heads 1412 are of different sizes.

FIG. 37 illustrates an angle at which a resection electrode head 1412may be arranged on electrode support 1408 with respect to thelongitudinal axis 1406′ of resection unit 1406. According to certainembodiments, resection electrode heads 1412 may be arranged on electrodesupport 1408 at an angle in the range of from 0° to about 175° withrespect to longitudinal axis 1406′. In embodiments having first andsecond parallel arrays of resection electrode heads 1412, e.g., FIG.36E, first array 1412 a is preferably arranged at an angle α in therange of from about 90° to 170°, and more preferably from about 105° to165°. Second array 1412 b is preferably arranged at an angle β in therange of from about 10° to 90°, and more preferably from about 15° to75°.

FIG. 38A shows in plan view a resection electrode support 1408 arrangedon shaft distal end portion 1402 a, wherein electrode support 1408includes resection electrode head 1412. FIGS. 38B-D each show a profileof a resection electrode head 1412 on an electrode support 1408 as seenalong the line 38B-D of FIG. 38A. From an examination of FIGS. 38B-D itcan be readily seen that, according to certain embodiments of theinvention, resection electrode head 1412 may protrude a significantdistance from the external surface of shaft 1402. Typically, eachresection electrode head 1412 protrudes from resection electrode support1408 by a distance in the range of from about 0.1 to 20 mm, andpreferably by a distance in the range of from about 0.2 to 10 mm.Resection electrode head 1412 may have a profile which is substantiallysquare or rectangular; arched or semicircular; or angular and pointed,as represented by FIGS. 38B-D, respectively. Other profiles and shapesfor resection electrode head 1412 are also within the scope of theinvention. Only one resection electrode head 1412 is depicted perelectrode support 1408 in FIGS. 38A-D. However, according to theinvention, each electrode support 1408 may have a plurality of resectionelectrode heads 1412 arranged thereon in a variety of arrangements (see,e.g., FIGS. 36A-F).

In the embodiments of FIGS. 38B-D, each electrode head 1412 is in theform of a filament or wire of electrically conductive material. In oneembodiment, the filament or wire comprises a metal. Such a metal ispreferably a durable, corrosion resistant metal. Suitable metals forconstruction of resection electrode head 1412 include, withoutlimitation, tungsten, stainless steel alloys, platinum or its alloys,titanium or its alloys, molybdenum or its alloys, and nickel or itsalloys. In embodiments wherein each electrode head 1412 is in the formof a filament or wire, the diameter of the wire is preferably in therange of from about 0.05 mm to about 5 mm, more preferably in the rangeof from about 0.1 to about 2 mm.

FIGS. 39A-I each show a cross-section of the filament or wire ofresection electrode head 1412 as seen, for example, along the lines39A-I of FIG. 38B. Evidently, a variety of different cross-sectionalshapes for resection electrode head 1412 are possible. For example,resection electrode head 1412 may be substantially round or circular,substantially square, or substantially triangular in cross-section, asdepicted in FIGS. 39A-C, respectively. Resection electrode head 1412 mayhave a cross-section having at least one curved side. For example, head1412 d of FIG. 39D has two substantially parallel sides and two concavesides. Head 1412 e of FIG. 39E has four concave sides forming fourcusps, while head 1412 f (FIG. 39F) includes three concave sides formingthree cusps.

FIGS. 39G-I each depict a cross-section of a wire or filament havingserrations on at least one side thereof. Resection electrode head 1412 gcomprises a filament having a substantially circular cross-section,wherein the circumference of the filament is serrated. In anotherembodiment (not shown) a selected portion of the circumference of asubstantially round filament may be serrated. Resection electrode head1412 h (FIG. 39H) comprises a filament having a substantially squarecross-section, wherein a leading or cutting edge portion 1413 h of thefilament is serrated. FIG. 39I shows a head 1412 i comprising a filamentof an electrically conductive material having a substantiallycrescent-shaped or semi-circular cross-sectional shape, wherein cuttingedge portion 1413 i is serrated. In addition, other cross-sectionalshapes for electrode head 1412 are contemplated and are within the scopeof the invention. Preferably, the cross-sectional shape and otherfeatures of resection electrode head 1412 promote high current densitiesin the vicinity of resection electrode head 1412 following applicationof a high frequency voltage to resection electrode head 1412. Morepreferably, the cross-sectional shape and other features of resectionelectrode head 1412 promote high current densities in the vicinity of aleading or cutting edge, e.g., edge 1413 h, 1413 i, of resectionelectrode head 1412 following application of a high frequency voltage toresection electrode head 1412. As noted previously, high currentdensities promote generation of a plasma in the presence of anelectrically conductive fluid, and the plasma in turn efficientlyablates tissue via the Coblation® procedure or mechanism. Preferably,the cross-sectional shape and other features of resection electrode head1412 are also adapted for maintenance of the plasma in the presence of astream of fluid passing over resection electrode head 1412. In oneembodiment, the cross-sectional shape and other features of resectionelectrode head 1412 are also adapted for the efficient mechanicalresection, abrading, or severing of, at least, soft tissue (such asskeletal muscle, skin, cartilage, etc.).

In one embodiment a cutting edge, e.g., edge 1413 h, 1413 i, is adaptedfor both ablating and resecting tissue. Depending on the embodiment,cutting edge 1413 h, 1413 i may be oriented, or point, in variousdirections relative to the longitudinal axis of shaft 1402. For example,depending on the particular embodiment of probe 1400, and on theparticular surgical procedure(s) for which embodiments of probe 1400 aredesigned to perform, cutting edge 1413 h, 1413 i may be orienteddistally, proximally, or laterally.

FIG. 40 shows a cross-section of a resection electrode head 1412,according to another embodiment of the invention, wherein head 1412includes a cutting edge 1413, and an insulating layer 1414 disposed on acovered portion of head 1412, and wherein cutting edge 1413 is free frominsulating layer 1414. Cutting edge 1413 promotes high current densitiesin a region between resection electrode head 1412 and the target siteupon application of a high frequency voltage to resection electrode head1412. At the same time, insulating layer 1414 reduces undesirablecurrent flow into tissue or surrounding electrically conducting liquidsfrom covered (insulated) portion of resection electrode head 1412. Theapplication or deposition of insulating layer 1414 to resectionelectrode head 1412 may be achieved by for example, thin-film depositionof an insulating material using evaporative or sputtering techniques,well known in the art. Insulating layer 1414 provides an electricallyinsulated non-active portion of resection electrode head 1412, therebyallowing the surgeon to selectively resect and/or ablate tissue, whileminimizing necrosis or ablation of surrounding non-target tissue orother body structures.

FIG. 41A illustrates a distal end of an electrosurgical probe showing inplan view resection electrode support 1408 including a plurality ofresection electrode heads 1412′, according to another embodiment of theinvention. In contrast to resection electrode heads 1412 describedhereinabove, each resection electrode head 1412′ in the embodiment ofFIGS. 41A-C is in the form of a blade. In one embodiment, each resectionelectrode head 1412′ may have a covered portion having an insulatinglayer thereon (analogous to insulating layer 1414 of resection electrodehead 1412 of FIG. 40). Resection electrode heads 1412′ are depicted inFIG. 41A as being arranged in a pair of angled parallel electrode headarrays. However, other arrangements for resection electrode heads 1412′are within the scope of the invention. FIG. 41B shows resectionelectrode heads 1412′ as seen along the lines 41B—41B of FIG. 41A. Eachresection electrode head 1412′ may include a cutting edge 1413′ adaptedfor promoting high current density in the vicinity of each resectionelectrode head 1412′ upon application of a high frequency voltagethereto. In one embodiment, cutting edge 1413′ is also adapted forsevering or mechanical resection of tissue. In one embodiment, cuttingedge 1413′ is serrated. Cutting edge 1413′ is shown in FIG. 41B asfacing away from shaft distal end portion 1402 a. However, in ananalogous situation to that described hereinabove with reference toFIGS. 39H-I, various embodiments of probe 1400 may have cutting edge1413′ facing in any direction with respect to the longitudinal axis ofshaft 1402, e.g., cutting edge 1413′ may face distally, proximally, orlaterally. Thus, probe 1400 may be provided in a form suitable forperforming a broad range of resection and ablation procedures.

FIG. 41C illustrates shaft distal end 1402 a of electrosurgical probe1400, taken along the lines 41C—41C of FIG. 41A, showing resectionelectrode heads 1412′ on resection electrode support 1408. From anexamination of FIGS. 41B-C it can be readily appreciated that, accordingto certain embodiments of the invention, resection electrode heads 1412′may protrude a significant distance from the external surface of shaft1402. Typically, each resection electrode head 1412′ protrudes fromresection electrode support 1408 by a distance in the range of fromabout 0.1 to 20 mm, and preferably by a distance in the range of fromabout 0.2 to 10 mm. Each resection electrode head 1412′ may comprise ametal blade, wherein the metal blade comprises a metal such as tungsten,stainless steel alloys, platinum or its alloys, titanium or its alloys,molybdenum or its alloys, nickel or its alloys, and the like.

FIG. 42A is a sectional view of shaft 1402 including distal end portion1402 a. Shaft 1402 includes resection unit 1406 and fluid delivery port1430 for supplying electrically conductive fluid to resection unit 1406via fluid delivery lumen 1432. A plurality of aspiration ports 1440 arelocated proximal to resection unit 1406. Aspiration ports 1440 lead toaspiration lumen 1442. Applicants have determined that positioningaspiration ports somewhat distant from resection unit 1406 and deliveryport 1430, the dwell time of the electrically conductive fluid isincreased, and a plasma can be created more aggressively andconsistently. Advantageously, by moving the aspiration ports somewhatdistant from the target site, suction will primarily aspirate excess orunwanted fluids (e.g., tissue fluids, blood, etc.) and gaseous ablationby-products from the target site, while the electrically conductivefluid, such as isotonic saline, remains at the target site.Consequently, less conductive fluid and tissue fragments are aspiratedfrom the target site, and entry of resected tissue fragments intoaspiration lumen 1442 is less likely to occur.

In the embodiments of FIGS. 42A-B, aspiration lumen 1442 includes atleast one digestion electrode 1450. More preferably, aspiration lumen1442 includes a plurality of digestion electrodes 1450. Each digestionelectrode 1450 serves as an active (ablation) electrode and is coupledto a high frequency power supply (e.g. power supply 428 of FIG. 7). Eachdigestion electrode 1450 is adapted for rapidly breaking down any tissuefragments that may be drawn into aspiration lumen 1442 during aresection and ablation procedure. In this manner, lumen 1442 remainsfree from blockage, and allows a surgical procedure to be completedconveniently and efficiently without interruption to either unblocklumen 1442 or to replace probe 1400. The shape, arrangement, size, andnumber, of digestion electrodes 1450 is to some extent a matter ofdesign choice. Preferably, each digestion electrode 1450 is adapted toprovide a high current density upon application thereto of a highfrequency voltage, thereby promoting rapid and efficient ablation ofresected tissue fragments.

In one embodiment, a plurality of digestion electrodes 1450 of asuitable shape and size may be arranged within aspiration lumen 1442such that digestion electrodes 1450 at least partially overlap orinterweave. Such overlapping digestion electrodes 1450 may act, at leastto some extent, as a screen to mechanically restrain tissue fragmentsthereat. While tissue fragments are restrained against one or moredigestion electrodes 1450, the latter may efficiently ablate the formerto yield low molecular weight ablation by-products which readily passthrough lumen 1442 in the aspiration stream. FIG. 42B illustrates intransverse section shaft 1402 taken along the lines 42B—42B of FIG. 42A,and showing fluid delivery lumen 1432 and aspiration lumen 1442, thelatter having digestion electrodes 1450 arranged therein. In thisembodiment, digestion electrodes 1450 are shown as having pointedsurfaces, such as are known to promote high current densities thereat,and digestion electrodes 1450 at least partially interweave with eachother.

FIGS. 43A-D are side views of shaft distal end portion 1402 a of anelectrosurgical probe 1400. FIG. 43A shows resection electrode support1408 disposed laterally on a linear or substantially linear shaft distalend 1402 a. FIG. 43B shows resection electrode support 1408 disposed onthe terminus of shaft 1402, wherein shaft distal end 1402 a includes abend or curve. In the embodiments of FIGS. 43A, 43B, electrode support1408 protrudes from an external surface of shaft distal end portion 1402a. Typically, electrode support 1408 protrudes a distance in the rangeof from about 0 (zero) to about 20 mm from the external surface of shaft1402. Each resection electrode support 1408 of the invention includes atleast one resection electrode terminal or head 1412/1412′. Eachresection electrode head 1412/1412′ is coupled, e.g. via a connectionblock and connecting cable, to a high frequency power supply unit,essentially as described hereinabove. However, for the sake of clarity,resection electrode head(s) 1412/1412′ are omitted from FIGS. 43A-D.

FIG. 43C shows shaft 1402 having resection electrode support 1408countersunk or recessed within shaft distal end 1402 a. In thisembodiment, an external surface of resection electrode support 1408 maybe aligned, or flush, with an external surface of shaft 1402. In thisembodiment, resection electrode heads 1412/1412′ (FIGS. 38B-D, 41A-C)may protrude from the external surface of shaft distal end 1402 a tovarious extents, as described hereinabove. FIG. 43D shows a shaft distalend portion 1402 having a depression or cavity 1416 therein. In thisembodiment, resection electrode support 1408 is housed within cavity1416. In this embodiment, resection electrode heads 1412/1412′ may, ormay not, extend above cavity 1416 and from the shaft external surface.In this embodiment the extent, if any, to which resection electrodeheads 1412/1412′ extend above cavity 1416 is determined by the depth ofcavity 1416, as well as by the height of resection electrode support1408, and the height of resection electrode heads 1412/1412′. Theembodiment of FIG. 43D serves to isolate non-target tissue fromresection electrode heads 1412/1412′, thereby minimizing collateraldamage to such tissue during a resection and ablation procedure.

Referring now to FIGS. 44A-D, a fluid delivery device for delivering anelectrically conductive fluid to resection unit 1406 or to tissue at atarget site can include a single fluid delivery port 1430 (e.g., FIG.34A) or a plurality of ports 1430. In exemplary embodiments of probe1400, ports 1430 are disposed around a perimeter of resection unit 1406,and are positioned to deliver the conductive fluid to resectionelectrode head(s) 1412/1412′. As shown in FIG. 44A, a plurality of ports1430 may be arranged around a distal portion of resection unit 1406. Inthe embodiment of FIG. 44B a plurality of ports 1430 are arranged aroundthe entire perimeter of resection unit 1406. The arrows shown in FIG.44B indicate a direction in which an electrically conductive fluid maybe delivered from the plurality of fluid delivery ports 1430. In oneembodiment, fluid delivery ports 1430 are rounded or substantiallycircular in outline.

As shown in FIG. 44C, a fluid delivery port 1430′ may be in the form ofan elongated opening or slit extending around a distal portion ofresection unit 1406. In the embodiment of FIG. 44D port 1430′ is in theform of a single slit extending around the perimeter of resection unit1406. In each embodiment (FIGS. 44A-D), delivery ports 1430/1430′preferably deliver electrically conductive fluid in the direction ofresection unit 1406. The amount of electrically conductive fluiddelivered to resection unit 1406, and the timing or periodicity of suchfluid delivery, may be controlled by an operator (surgeon). In oneembodiment, the amount of electrically conductive fluid delivered toresection unit 1406 is sufficient to, at least transiently, immerseresection electrode heads 1412/1412′ in the electrically conductivefluid.

FIG. 45 shows a shaft distal end portion 1402 a of shaft 1402, accordingto one embodiment of the invention. In this embodiment, resection unit1406/resection electrode support 1408 is disposed on return electrode1420, wherein return electrode 1420 comprises an exposed region of shaft1402. By “exposed region” is meant a region of shaft distal end portion1402 a which is not covered by an insulating sleeve or sheath 1460.Insulating sleeve 1460 may comprise a layer or coating of a flexibleinsulating material, such as various plastics (e.g., a polyimide orpolytetrafluoroethylene, and the like) as is well known in the art. Inthis embodiment, a plurality of fluid delivery ports 1430 are positionedwithin return electrode 1420 such that when the electrically conductivefluid contacts resection electrode heads 1412/1412′ on resectionelectrode support 1408, an electrical circuit, or current flow path, iscompleted. A plurality of aspiration ports 1440 are spaced proximallyfrom resection electrode support 1408 for removing unwanted fluids, suchas ablation by-products, from the vicinity of resection unit 1406.Resection electrode support 1408 may be substantially square,rectangular, oval, circular, etc. Typically, resection electrode support1408 has a dimension in the longitudinal direction of the shaft (i.e., alength) in the range of from about 1 mm to about 20 mm, more typicallyin the range of from about 2 mm to about 10 mm.

Referring now to FIG. 46, a surgical kit 1500 for resecting and/orablating tissue according to the invention will now be described. FIG.46 schematically represents surgical kit 1500 including electrosurgicalprobe 1400, a package 1502 for housing probe 1400, a surgical instrument1504, and an instructions for use 1506. Instructions for use 1506include instructions for using probe 1400 in conjunction with apparatusancillary to probe 1400, such as power supply 428 (FIG. 7). Package 1502may comprise any suitable package, such as a box, carton, etc. In anexemplary embodiment, package 1502 includes a sterile wrap or wrapping1504 for maintaining probe 1400 under aseptic conditions prior toperforming a surgical procedure.

An electrosurgical probe 1400 of kit 1500 may comprise any of theembodiments described hereinabove. For example, probe 1400 of kit 1500may include shaft 1402 having at least one resection electrode 1410 atshaft distal end 1402 a, and at least one connector (not shown)extending from the at least one resection electrode 1410 to shaftproximal end 1402 b for coupling resection electrode 1410 to a powersupply. Probe 1400 and kit 1500 are disposable after a single procedure.Probe 1400 may or may not include a return electrode 1420.

Instructions for use 1506 generally includes, without limitation,instructions for performing the steps of: adjusting a voltage level of ahigh frequency power supply to effect resection and/or ablation oftissue at the target site; connecting probe 1400 to the high frequencypower supply; positioning shaft distal end 1402 a within an electricallyconductive fluid at or near the tissue at the target site; andactivating the power supply to effect resection and/or ablation of thetissue at the target site. An appropriate voltage level of the powersupply is usually in the range of from about 40 to 400 volts rms foroperating frequencies of about 100 to 200 kHz. Instructions 1506 mayfurther include instruction for advancing shaft 1402 towards the tissueat the target site, and for moving shaft distal end portion 1402 a inrelation to the tissue. Such movement may be performed with or withoutthe exertion of a certain mechanical force on the target tissue viaresection unit 1406, depending on parameters such as the nature of theprocedure to be performed, the type of tissue at the target site, therate at which the tissue is to be removed, and the particular design orembodiment of probe 1400/resection unit 1406.

FIGS. 47A-B schematically represent a method of performing a resectionand ablation electrosurgical procedure, according to another embodimentof the invention, wherein step 1600 (FIG. 47A) involves providing anelectrosurgical probe having a resection unit. The probe provided instep 1600 includes a shaft distal end, wherein the resection unit isdisposed at the shaft distal end, either laterally or terminally. Theresection unit includes an electrode support comprising an insulatingmaterial and at least one resection electrode head arranged on theelectrode support. Step 1602 involves adjusting a voltage level of apower supply, wherein the power supply is capable of providing a highfrequency voltage of a selected voltage level and frequency. The voltageselected is typically between about 5 kHz and 20 MHz, essentially asdescribed hereinabove. The RMS voltage will usually be in the range offrom about 5 volts to 1000 volts, and the peak-to-peak voltage will bein the range of from about 10 to 2000 volts, again as describedhereinabove. The actual or preferred voltage will depend on a number offactors, including the number and size of resection electrodescomprising the resection unit.

Step 1604 involves coupling the probe to the power supply unit. Step1606 involves advancing the resection unit towards tissue at a targetsite whence tissue is to be removed. In optional step 1608, a quantityof an electrically conductive fluid may be applied to the resection unitand/or to the target site. For performance of a resection and ablationprocedure in a dry field, optional step 1608 is typically included inthe procedure. Step 1608 may involve the application of a quantity of anelectrically conductive fluid, such as isotonic saline, to the targetsite. The quantity of an electrically conductive fluid may be controlledby the operator of the probe. The quantity of an electrically conductivefluid applied in step 1608 may be sufficient to completely immerse theresection unit and/or to completely immerse the tissue at the targetsite. Step 1610 involves applying a high frequency voltage to theresection unit via the power supply unit. Step 1612 involves contactingthe tissue at the target site with the resection unit.

With reference to FIG. 47B, optional step 1614 involves exertingpressure on the tissue at the target site by applying a force to theprobe, while the resection unit is in contact with the tissue at thetarget site, in order to effect resection of tissue. Typically, such aforce is applied manually by the operator (surgeon), although mechanicalapplication of a force to the probe, e.g., by a robotic arm undercomputer control, is also possible. The amount of any force applied inoptional step 1614 will depend on factors such as the nature of thetissue to be removed, the design or embodiment of the probe, and theamount of tissue to be resected. For example, in the absence of anymechanical force applied to the tissue, tissue removal from the targetsite is primarily or solely by ablation. On the other hand, with theelectrical power turned off, either transiently or for all or a portionof a procedure, the probe may be used for mechanical resection oftissue. Typically, however, the probe is used for the concurrentelectrical ablation and mechanical resection of tissue.

Step 1616 involves moving the resection unit of the probe with respectto the tissue at the target site. Typically, step 1616 involves movingthe resection unit and the at least one resection electrode head in adirection substantially perpendicular to a direction of any pressureexerted in step 1614, or in a direction substantially parallel to asurface of the tissue at the target site. Typically, step 1616 isperformed concurrently with one or more of steps 1608 through 1614. Inone embodiment, step 1616 involves repeatedly moving the resection unitwith respect to the tissue at the target site until an appropriatequantity of tissue has been removed from the target site. Typically, aportion of the tissue removed from the target site is in the form ofresected tissue fragments. Step 1618 involves aspirating the resectedtissue fragments from the target site via at least one aspiration porton the shaft, wherein the at least one aspiration port is coupled to anaspiration lumen. In one embodiment, the probe includes at least onedigestion electrode capable of aggressively ablating resected tissuefragments. Step 1620 involves ablating resected tissue fragments withthe at least one digestion electrode. In one embodiment, the at leastone digestion electrode is arranged within the aspiration lumen, and theresected tissue fragments are ablated within the aspiration lumen.

FIG. 48 schematically represents a method of making a resection andablation electrosurgical probe, according to the invention, wherein step1700 involves providing a shaft having a resection unit. The shaftprovided in step 1700 includes a shaft proximal end and a shaft distalend, wherein the resection unit is disposed at the shaft distal end,either laterally or terminally. In one embodiment, the shaft comprisesan electrically conductive lightweight metal cylinder. The resectionunit includes an electrode support comprising an insulating material andat least one resection electrode arranged on the electrode support. Eachresection electrode includes a resection electrode head. Each resectionelectrode head typically comprises a wire, filament, or blade of a hardor rigid, electrically conductive solid material, such as tungsten,stainless steel alloys, platinum or its alloys, titanium or its alloys,molybdenum or its alloys, nickel or its alloys, and the like.

Typically, the shaft provided in step 1700 further includes at least onedigestion electrode capable of aggressively ablating tissue fragments.In one embodiment, the at least one digestion electrode is arrangedwithin the aspiration lumen. Each digestion electrode typicallycomprises an electrically conductive metal, such as tungsten, stainlesssteel alloys, platinum or its alloys, titanium or its alloys, molybdenumor its alloys, nickel or its alloys, aluminum, gold, or copper, and thelike. Typically, the shaft provided in step 1700 further includes areturn electrode.

In one embodiment, the method includes step 1702 which involves encasinga portion of the shaft within an insulating sleeve to provide anelectrically insulated proximal portion of the shaft and an exposeddistal portion of the shaft. The exposed distal portion of the shaftdefines a return electrode of the probe. The insulating sleeve typicallycomprises a substantially cylindrical length of a flexible insulatingmaterial such as polytetrafluoroethylene, a polyimide, and the like.Such flexible insulating materials are well known in the art. In oneembodiment, the resection electrode support is disposed on the returnelectrode. The resection electrode support typically comprises anelectrically insulating material such as a glass, a ceramic, a silicone,a polyurethane, a urethane, a polyimide, silicon nitride, teflon,alumina, or the like. The electrode support serves to electricallyinsulate the at least one resection electrode head from the returnelectrode. Step 1704 involves providing a handle having a connectionblock. Step 1706 involves coupling the resection electrodes and thedigestion electrodes to the connection block. The connection blockprovides a convenient mechanism by which the resection and digestionelectrodes may be coupled to a high frequency power supply. Step 1708involves affixing the shaft proximal end to the handle.

There now follows a description, with reference to FIGS. 49-60B, of anelectrosurgical probe 1800 and associated electrosurgical system adaptedfor the aggressive removal of tissue during a broad range of surgicalprocedures. According to one aspect of the invention, probe 1800 differsfrom certain other probes described hereinbelow, and from conventionalprobes of the prior art, in that probe 1800 lacks a dedicated orpermanent return electrode. Furthermore, in use the electrosurgicalsystem of which probe 1800 is a part is not operated in conjunction witha non-integral return electrode (e.g., a dispersive pad). Rather, probe1800 includes a first electrode (or electrode type) and a secondelectrode (or electrode type), wherein each of the first electrode typeand the second electrode type is designed and adapted for having atissue-altering effect on a target tissue. That is to say, each of thefirst electrode type and the second electrode type can function as anactive electrode. Each of the first electrode type and the secondelectrode type can also function as a return electrode. In particular,the first electrode and the second electrode can alternate betweenserving as an active electrode and serving as a return electrode.Typically, when the first electrode serves as the active electrode, thesecond electrode serves as the return electrode; and when the secondelectrode serves as the active electrode, the first electrode serves asthe return electrode. In use, the first electrode and the secondelectrode are independently coupled to opposite poles of a highfrequency power supply to enable current flow therebetween. For example,the first electrode and the second electrode may be independentlycoupled to opposite poles of power supply 428 (FIG. 7), for supplyingalternating current to the first electrode and the second electrode.

Typically, the first electrode or electrode type comprises one or moreablation electrodes 1810, and the second electrode or electrode typecomprises one or more digestion electrodes 1820 (e.g., FIG. 49).According to one embodiment, at any given time point electric power isgenerally supplied preferentially to the first electrode or to thesecond electrode. That is to say, at any given time point the highfrequency power supply alternatively supplies most of the power toeither the first electrode or to the second electrode. In this manner,at any given time point either the first electrode or the secondelectrode may receive up to about 100% of the power from the powersupply. Typically, an electrode or electrode type which receives most ofthe power from the power supply receives from about 60% to about 100% ofthe power; and more typically from about 70% to about 100% of the power.The actual percentage of power preferentially received by one of the twoelectrode types at any given time point may vary according to a numberof factors, including: the power level or setting of the power supply,the electrical impedance of any tissue in the presence of the twoelectrode types, and the geometry of the two electrode types.

Typically, when only the ablation electrode is in contact with tissue,the ablation electrode preferentially receives electric power from thepower supply such that the ablation electrode functions as the activeelectrode and ablates tissue, e.g., at a target site targeted fortreatment. In this ablation mode, the digestion electrode normallyserves as a return electrode. Conversely, when only the digestionelectrode is in contact with tissue, the digestion electrode typicallyreceives the majority of the electric power from the power supply suchthat the digestion electrode functions as the active electrode and iscapable of ablating tissue (e.g., digesting tissue fragments resectedfrom the target site during the ablation mode). In this digestion mode,the ablation electrode normally serves as a return electrode.

Typically, when one of the two electrode types encounters tissue suchthat the milieu of that electrode type undergoes a change in electricalimpedance, while the other electrode type is not in contact with oradjacent to tissue in this manner, the former electrode typepreferentially receives power from the power supply. Typically, theelectrode type which preferentially receives power from the power supplyfunctions as active electrode and is capable of having a tissue-alteringeffect. Usually, only one of the two electrode types can function asactive electrode during any given time period. During that given timeperiod, the other, non-active electrode functions as a return electrodeand is incapable of having a tissue-altering effect. While not beingbound by theory, Applicants believe that the preferential delivery ofpower to one electrode type in the presence of tissue, while the otherelectrode type is not in the presence of tissue, is due to theelectrical impedance of the tissue causing relatively high currentdensities to be generated at the former electrode type.

In one mode of operation, both the first and second electrode types maybe in contact with tissue simultaneously. For example, an ablationelectrode of the probe may be in contact with tissue at a site targetedfor treatment, and at the same time the digestion electrode may be incontact with one or more fragments of tissue resected from the targetsite. If the ablation and digestion electrodes are both in contact withtissue at the same time but the electrodes have different surface areas,the available power may be supplied preferentially to one of the twoelectrode types. In particular, by arranging for an appropriate ablationelectrode:digestion electrode surface area ratio, when tissue is incontact with or in the vicinity of the digestion electrode, thedigestion electrode may receive the majority of the available electricpower and thus function as the active electrode. By arranging for anappropriate ablation electrode:digestion electrode surface area ratio, ashift from the ablation electrode serving as active electrode to thedigestion electrode serving as active electrode can be triggered by achange in electrical impedance in the vicinity of the digestionelectrode. Such a change in electrical impedance typically results fromthe presence of one or more tissue fragments, e.g. a tissue fragmentflowing towards the digestion electrode in an aspiration stream.According to one aspect of the invention, the ablationelectrode:digestion electrode surface area ratio is in the range of fromabout 3:1 to about 1.5:1.

According to the invention, the elimination of a conventional ordedicated return electrode from probe 1800 enables the active electrode,i.e., either the ablation electrode or the digestion electrode, toreceive up to 100%, of the power or current supplied by the highfrequency power supply. For convenience, the terms ablation electrodeand digestion electrode may be used hereafter in the singular form, itbeing understood that such terms include one, or more than one, ablationelectrode; and one, or more than one, digestion electrode, respectively.Ablation electrode 1810 is capable of aggressively removing tissue froma target site by a cool ablation mechanism (Coblation®), generally asdescribed hereinabove. Typically, the temperature of tissue subjected tocool ablation according to the instant invention is in the range of fromabout 45° C. to 90° C., and more typically in the range of from about60° C. to 70° C.

According to one embodiment, ablation electrode 1810 may be regarded asa default or primary active electrode, and as a back-up or secondaryreturn electrode; while digestion electrode 1820 may be regarded as adefault or primary return electrode and as a secondary active electrode.The active electrode (either electrode 1810 or electrode 1820, dependingon the mode of operation of the electrosurgical system) generates aplasma from an electrically conductive fluid present in the vicinity ofthe active electrode, and the plasma causes breakdown of tissue in theregion of the active electrode by molecular dissociation of tissuecomponents to form low molecular weight Coblation® by-products,essentially as described hereinabove. The return electrode completes acurrent flow path from the active electrode via the electricallyconductive fluid located therebetween, and has no significanttissue-altering effect while serving as the return electrode.

In one embodiment and according to one mode of operation of anelectrosurgical system of the invention, probe 1800 is configured suchthat only one of the two electrode types is in contact with tissue at atarget site. According to one aspect of the invention, probe 1800 isconfigured such that one of the two electrode types can be brought intocontact with tissue at a target site while the other of the twoelectrode types remains remote from the tissue at the target site.Typically, probe 1800 is configured such that ablation electrode 1810can be readily brought into contact with the tissue at the target site,while digestion electrode 1820 avoids contact with the tissue at thetarget site.

According to one aspect of the invention, when ablation electrode 1810is in the presence of tissue (e.g., at a target site) and in the absenceof tissue (e.g. resected tissue fragments) in the milieu of digestionelectrode 1820, electrodes 1810, 1820 may serve as default active andreturn electrodes, respectively. However, when tissue is present in themilieu of digestion electrode 1820, power from the power supply may beswitched from ablation electrode 1810 to digestion electrode 1820, suchthat electrode 1820 serves as an active electrode while ablationelectrode 1810 serves as the return electrode. In one aspect, such analternation, or reversal, of roles between electrodes 1810, 1820 may bea transient event. For example, in the presence of a resected tissuefragment, digestion electrode 1820 may preferentially receive power fromthe power supply and assume the role of active electrode, such that aplasma is generated in the vicinity of digestion electrode 1820, and theresected tissue fragment is broken down via Coblation® to form lowmolecular weight by-products. Thereafter, in the absence of tissue inthe milieu of digestion electrode 1820, electrode 1820 may rapidlyrevert to its role of default return electrode. At the same time,ablation electrode 1810 reverts to its role of default active electrode.The respective roles of electrodes 1810 and 1820 as active and returnelectrodes, respectively, may then continue until digestion electrode1820 again encounters tissue in its vicinity. In this manner, digestionelectrode 1820 generally only receives most of the power from the powersupply in the presence of tissue (e.g., a resected tissue fragment),while ablation electrode 1810 may preferentially receive power from thepower supply at all times other than when digestion electrode 1820preferentially receives power from the power supply.

While not being bound by theory, Applicants believe that thetransformation or “switch” of digestion electrode 1820, from serving asreturn electrode to serving as active electrode, may be mediated by achange in electrical impedance in the vicinity of digestion electrode1820, wherein the impedance change results from the presence of tissuein the electrically conductive fluid adjacent to electrode 1820. Again,while not being bound by theory, Applicants believe that the ratio ofthe surface area of the ablation electrode (Sa) to the surface area ofthe digestion electrode (Sd), Sa:Sd is a factor in causing electrodes1810 and 1820 to alternate between active/return electrode mode.Generally, the Sa: Sd ratio is in the range of from about 3.5:1 to about1:1, preferably in the range of from about 2.5:1 to about 1.5:1, andmore preferably about 2:1. By selecting a suitable Sa:Sd ratio for probe1800, as has been achieved by Applicants, the feature of alternatingbetween preferentially supplying power to ablation electrode 1810 andpreferentially supplying power to digestion electrode 1820 becomes aninherent characteristic of an electrosurgical system according to theinvention. An effective or optimum Sa:Sd ratio for bringing about ashift in preferentially supplying power to either ablation electrode1810 or digestion electrode 1820 may vary according to a number ofparameters including the volume of materials aspirated from a targetsite, and the velocity of an aspiration stream. Therefore, in someembodiments an aspiration stream control unit (not shown) may be used inconjunction with probe 1800 in order to quantitatively regulate theaspiration stream.

FIG. 49 shows a side view of an electrosurgical probe 1800 for use inconjunction with an electrosurgical system, according to one embodimentof the invention. Probe 1800 includes a handle 1804 and a shaft 1802having shaft distal end 1802 a and shaft proximal end 1802 b. In thisembodiment, ablation electrode 1810 and digestion electrode 1820 aremounted on the distal terminus 1806 of shaft 1802. However, lateralmounting of ablation electrode 1810 and digestion electrode 1820 is alsopossible under the invention. In light of the absence of a permanent ordedicated return electrode from probe 1800, shaft 1802 may comprise arigid insulating material, for example, various synthetic polymers,plastics, and the like, well known in the art. Alternatively, shaft 1802may comprise an electrically conducting solid material whose surface isentirely covered with an insulating material. Such electricallyconducting solid materials include various metals such as stainlesssteel, tungsten and its alloys, and the like. An insulating materialcovering shaft 1802 may comprise a flexible, electrically insulatingsleeve or jacket of a plastic material, such as a polyimide, and thelike. Typically, shaft 1802 has a length in the region of from about 5to 30 cm, more typically from about 7 to 25 cm, and most typically fromabout 10 to 20 cm. Generally, handle 1804 has a length in the range offrom about 2 to 10 cm.

FIG. 50A is a longitudinal section of probe 1800 including shaft distalend 1802 a having ablation electrode 1810 and digestion electrode 1820mounted at shaft distal terminus 1806. Handle 1804 includes a connectionblock 1805. Ablation electrode 1810 and digestion electrode 1820 areconnected to connection block 1805 via ablation electrode lead 1811 anddigestion electrode lead 1821, respectively. Leads 1811, 1821 enableablation electrode 1810 and digestion electrode 1820 to be coupled to apower supply independently of each other, such that ablation electrode1810 and digestion electrode 1820 can independently receive power fromthe power supply. Connection block 1805 provides a convenient mechanismfor coupling electrodes 1810, 1820 to the power supply, e.g., via one ormore connecting cables (see, e.g., FIG. 7). Probe 1800 of FIG. 50A alsoincludes an aspiration device, namely a terminal aspiration port 1840,an aspiration lumen 1842 leading proximally from port 1840, and anaspiration tube 1844 coupled to lumen 1842. Tube 1844 may be coupled toa vacuum source, for applying a vacuum or partial vacuum to port 1840,and to a collection reservoir for collecting aspirated materials, as iswell known in the art.

FIG. 50B is an end view of shaft distal terminus 1806 of FIG. 50A, asseen along the lines 50B—50B of FIG. 50A. In FIG. 50B, ablationelectrode 1810 and digestion electrode 18200 are each represented as arectangular box located at approximately 12 o'clock and six o'clock,respectively, on either side of a substantially centrally locatedaspiration port 1840. However, various other shapes, number,arrangements, etc. for electrodes 1810, 1820 and aspiration port 1840are contemplated under the invention, as is described in enabling detailhereinbelow. Each of ablation electrode 1810 and digestion electrode1820 may be constructed from a material comprising a metal such astungsten, stainless steel alloys, platinum or its alloys, titanium orits alloys, molybdenum or its alloys, nickel or its alloys, aluminum,gold, or copper, and the like. A currently preferred material forconstruction of ablation electrode 1810 and digestion electrode 1820 isplatinum or various of its alloys.

FIG. 51A shows a longitudinal section of shaft distal end 1802 a ofprobe 1800, according to another embodiment of the invention, whereinablation electrode 1810 is mounted on shaft distal terminus 1806. Shaftdistal end 1402 a includes port 1440 leading to aspiration lumen 1442.In this embodiment, digestion electrode 1820 is mounted proximal toablation electrode 1810 within lumen 1442. Digestion electrode 1820 isshown in FIG. 51A as being mounted in the distal region of lumen 1442adjacent to port 1440, however, according to certain embodiments of theinvention, ablation electrode 1810 may be located within lumen 1442 moredistant from port 1440. In this configuration, ablation electrode 1810may be readily brought into contact with tissue at a site targeted fortreatment, while digestion electrode 1820 does not contact the tissue atthe target site and electrode 1820 remains remote from the target site.

Ablation electrode 1810 and digestion electrode 1820 have ablationelectrode lead 1811 and digestion electrode lead 1821, respectively.Ablation electrode lead 1811 and digestion electrode lead 1821 may becoupled to connection block 1805, substantially as described withreference to FIG. 50A. FIG. 51B shows an end view of distal terminus1806 of electrosurgical probe 1800, taken along the lines 51B—51B ofFIG. 51A. Ablation electrode 1810 and digestion electrode 1820 are eachrepresented as a rectangular box, wherein digestion electrode 1820 islocated at approximately six o'clock within aspiration lumen 1842.However, various other shapes, locations, etc. for electrodes 1810, 1820are possible under the invention. A plurality of fluid delivery ports1830 are also located on shaft distal terminus 1806 adjacent to ablationelectrode 1810. Ports 1830 serve to deliver electrically conductivefluid to tissue at a target site, or to ablation electrode 1810 beforeor during a surgical procedure, e.g., as described hereinabove withreference to FIGS. 34A, 44A-D. Although two ports 1830 are shown in FIG.51B as being substantially ovoid, other shapes, arrangements, andnumbers of ports 1830 are also within the scope of the invention.

FIG. 52A is a longitudinal section of a probe 1800, according to anotherembodiment of the invention, in which ablation electrode 1810 anddigestion 1820 are mounted on an electrode support 1808 at shaft distalterminus 1806. Ablation and digestion electrode leads 1811, 1821 areomitted for the sake of clarity. FIG. 52B is an end view of shaft distalterminus 1806, taken along the lines 52B—52B of FIG. 52A. Support 1808includes a central bore or void 1840′ (FIGS. 53B-D), wherein bore 1840′defines an opening to aspiration port 1840/lumen 1842. Ablationelectrode 1810 and digestion electrode 1820 are shown in FIG. 52A asbeing in the same plane or substantially the same plane. However,according to various alternative embodiments of the invention, ablationand digestion electrodes 1810, 1820 may be in different planes.Typically, ablation and digestion electrodes 1810, 1820 are in the sameplane, or digestion electrode 1820 is located proximal to ablationelectrode 1810 In the former situation, (i.e., ablation and digestionelectrodes 1810, 1820 are in the same plane) by advancing probe 1800towards the target site at a suitable angle, ablation electrode 1810 maycontact the tissue at the target site while digestion electrode 1820avoids contact with the tissue. In the latter situation (i.e., digestionelectrode 1820 is located proximal to ablation electrode 1810 (e.g.,FIGS. 51A, 57A)), probe 1800 is configured such that digestion electrode1820 easily avoids contact with tissue at a site targeted for resectionby ablation electrode 1810, regardless of the angle at which probe 1800approaches the tissue.

The structure of an electrode support 1808 according to a currentlypreferred embodiment is perhaps best seen in FIGS. 53A-D. FIG. 53A showssupport 1808, unmounted on shaft 1802, as seen from the side. FIG. 53Bis a perspective view of support 1808, including bore 1840′ and afrusto-conical distal surface 1809. FIG. 53C is a face or end view ofsupport 1808 showing bore 1840′, and frusto-conical distal surface 1809.Support 1808 may include one or more mounting holes 1807 adapted formounting support 1808 to shaft 1802, or for mounting ablation anddigestion electrodes 1810, 1820 to support 1808. Mounting holes 1807 mayalso be used for passing electrode leads 1811, 1821, therethrough.Although four mounting holes 1807 are shown substantially equidistantfrom each other in FIG. 53C, other numbers and arrangements of mountingholes 1807 are possible under the invention. In some embodiments,mounting holes 1807 are strategically located on support 1808, forexample, to specifically accommodate the precise size, number, andarrangement of electrodes to be mounted or affixed thereto. FIG. 53D isa sectional view of support 1808 taken along the lines 53D—53D of FIG.53C illustrating the geometry of support 1808 including surface 1809. Insome embodiments, ablation electrode 1810 may be mounted on surface1809. In certain embodiments, both ablation electrode 1810 and digestionelectrode 1820 may be mounted on surface 1809. Support 1808 may comprisea rigid or substantially rigid, durable or refractory insulatingmaterial. In one embodiment, support 1808 comprises a material such as aceramic, a glass, a silicone, or the like.

FIG. 54 shows a sectional view of electrode support 1808 of anelectrosurgical probe 1800, in which a portion of frusto-conical surface1809 (see, e.g., FIG. 53B) has been removed to provide a narrowerfrusto-conical surface 1809 a and a recessed surface 1809′. In thisembodiment, ablation electrode 1810 may be mounted on a distal portionof surface 1809 for making facile contact with tissue to be treated orremoved, Such an arrangement for ablation electrode 1810 promotes rapidand aggressive tissue removal from a target site. Digestion electrode1820, in contrast, may be disposed on recessed surface 1809′ to avoiddirect contact of electrode 1820 with tissue. As described hereinabove,the presence of tissue in the vicinity of digestion electrode 1820 maytrigger the switching of electric power from ablation electrode 1810 todigestion electrode 1820. By avoiding direct contact of electrode 1820with tissue at a site targeted for treatment, digestion electrode 1820is prevented from preferentially receiving electric power from the powersupply over an extended time period. This situation is undesirable inthat when the digestion electrode 1820 preferentially receives electricpower (i.e., functions as active electrode), there is concomitanttransfer of electric power away from ablation electrode 1810. Underthese circumstances, ablation electrode 1810 functions as returnelectrode, and consequently tissue at the target site is not efficientlyremoved via the cool ablation mechanism of the invention.

FIG. 55 shows a sectional view of electrode support 1808 of anelectrosurgical probe 1800 in which a groove 1814 is formed infrusto-conical surface 1809 (see, e.g., FIG. 53B) to provide an outersurface 1809 a and an inner surface 1809 b. In this embodiment, ablationelectrode 1810 may be mounted on outer surface 1809 a for making facilecontact with tissue and efficient tissue removal, essentially asdescribed with reference to FIG. 54. In the embodiment of FIG. 55,however, digestion electrode 1820 is disposed within groove 1814. Inthis manner, electrode 1820 avoids routine contact with tissue, andprobe 1800 of FIG. 55 enjoys the advantages expounded with respect tothe embodiment of FIG. 54, namely the futile reversal of role ofelectrodes 1810, 1820 triggered by tissue in the presence of electrode1820.

FIG. 56A shows, in longitudinal section, a shaft distal end 1802 a of anelectrosurgical probe 1800, according to another embodiment of theinvention, wherein digestion electrode 1820 is disposed on support 1808and extends across aspiration port 1840/bore 1840′. In one embodiment,digestion electrode 1820 has a first end attached to electrode lead 1821(e.g., FIGS. 57A, 57B), and a second free end. In another embodiment,digestion electrode 1820 is in the form of a flat wire or metal ribbon(e.g., FIG. 58). Ablation electrode 1810 is located on surface 1809 ofsupport 1808 distal to digestion electrode 1820. FIG. 56B shows thedistal end of probe 1800, taken along the lines 56B—56B of FIG. 56A,illustrating a plurality of attachment units 1822 for affixing electrode1810 to support 1808. In this embodiment, support 1808 occupies themajority of shaft distal terminus 1806. Ablation electrode 1810 ismounted on support 1808, has a substantially semi-circular shape, andpartially surrounds aspiration port 1840. FIG. 56C is a side view ofshaft distal end 1802 a showing attachment of ablation electrode 1810 toelectrode support 1808, according to one embodiment of the invention.Although FIG. 56C shows ablation electrode 1810 affixed to electrodesupport 1808 via ball wires, other attachment methods are also withinthe scope of the invention. Methods for attachment of electricallyconductive solids (e.g., metals) to insulating solid supports are wellknown in the art. Ablation electrode 1810 is coupled to connection block1805 via electrode lead 1811. Lead 1811 may pass through mounting hole1807.

FIG. 57A shows a longitudinal section of shaft distal end 1802 a of aprobe 1800, according to another embodiment of the invention. In thisembodiment, digestion electrode 1820 is arranged within aspiration lumen1842. Ablation electrode 1810 is located distal to aspiration port 1840and is coupled to lead 1811. FIG. 57B shows, in end view, the distal endportion 1802 a of probe 1800, taken along the lines 57B—57B of FIG. 57A.Digestion electrode 1820 of FIGS. 57A, 57B is in the form of a flat wireor metal ribbon. Electrode 1820 has a first end 1820 a and a second freeend 1820 b. First end 1820 a is connected to lead 1821 (FIG. 57A). Incontrast, in this embodiment, free end 1820 b terminates withoutcontacting an electrically conductive material, for example free end1820 b terminates in a wall of aspiration lumen 1842, wherein lumen 1842comprises an electrically insulating material. As an example, lumen 1842may comprise a plastic tube or cylinder having electrically insulatingproperties. By arranging for free end 1820 b to dead-end or terminatewithout contacting an electrically conductive material, Applicants havefound improved generation and maintenance of a plasma in the vicinity ofelectrode 1820 upon application of a suitable high frequency voltagethereto. As is described fully hereinabove, the presence of a plasma isa key factor in efficient ablation of tissues via the cool ablation(Coblation®) mechanism of the invention. Without intending to be boundin any way by theory, Applicants believe that by arranging for free end1820 b to terminate without contacting an electrically conductivematerial, when electric power is preferentially supplied to electrode1820, distribution of power along the length of electrode 1820 isasymmetric and is highly concentrated at certain locations. In this way,localized high current densities are produced in the vicinity of someregion(s) of electrode 1820, thereby promoting plasma formation.

FIG. 58 is a perspective view of a digestion electrode 1820, accordingto one embodiment of the invention. Although electrode 1820 is shown ashaving an arch shape, other shapes including planar or flat, circular orrounded, helical, etc., are also within the scope of the invention.Similarly, although electrode 1820 is shown as a flat wire or ribbon,i.e., as having a substantially rectangular cross-sectional shape, manyother cross-sectional shapes for electrode 1820 are also possible underthe invention. As an example, electrode 1820 may have one or more of thecross-sectional shapes described hereinabove, for example, withreference to FIGS. 39A-I.

FIG. 59A shows, in longitudinal section, shaft distal end 1802 a of anelectrosurgical probe 1800, wherein ablation electrode 1810 is mountedlaterally on shaft 1802. In this embodiment, shaft distal terminus 1806may have a rounded shape. Ablation electrode 1810 is coupled to lead1811 for connecting electrode 1810 to connection block 1805. Digestionelectrode 1820 is disposed proximal to ablation electrode 1810 withinaspiration lumen 1842. FIG. 59B shows shaft distal end 1802 a of FIG.59A in plan view. Ablation electrode 1810 may be mounted on an electrodesupport (e.g., FIGS. 60A-B). Ablation electrode 1810 and digestionelectrode 1820 are each represented in FIGS. 52A-B as a rectangular box.However, various other shapes, locations, etc. for electrodes 1810, 1820are possible under the invention.

FIG. 60A shows a plan view of shaft distal end 1802 a of anelectrosurgical probe 1800, having ablation and digestion electrodes1810, 1820 mounted laterally on shaft distal end 1802 a, according toanother embodiment of the invention. Ablation electrode 1810 partiallyencircles aspiration port 1840, and is mounted on electrode support1808. Electrode support 1808 may be a hard or durable electricallyinsulating material of the type described hereinabove. A pair ofdigestion electrodes 1820 are disposed proximal to ablation electrode1810 and extend across port 1840. FIG. 60B shows a transversecross-section of shaft distal end 1802 a taken along the lines 60B—60Bof FIG. 60A. Ablation electrode 1810 may be in the form of a metalscreen, a metal plate, a wire, or a metal ribbon. In one embodiment,ablation electrode 1810 may comprise a semicircular screen or platecomprising platinum or one of its alloys. Digestion electrode 1820 maybe a wire or metal ribbon which may be straight, twisted, looped invarious directions, or helical. In one embodiment, digestion electrode1820 is a ribbon or flattened wire comprising platinum or one of itsalloys. Other compositions, numbers, shapes and arrangements of ablationelectrode 1810 and digestion electrode 1820 are also within the scope ofthe invention. A fluid delivery port 1830 is located proximal toablation electrode 1810. Port 1830 serves to deliver electricallyconductive fluid to tissue at a target site or to ablation electrode1810 before or during a surgical procedure. Although port 1830 is shownin FIG. 60A as being substantially crescent shaped, other shapes,arrangements, and numbers of port 1830 are also within the scope of theinvention.

FIG. 61 schematically represents a series of steps involved in a methodof removing tissue from a target site to be treated using anelectrosurgical system, according to another embodiment of theinvention, wherein step 1900 involves coupling an electrosurgical probeto a power supply unit. The probe may be a probe having the elements,structures, features or characteristics described herein, e.g., withreference to FIG. 49 through FIG. 60B. In particular the probe, has twotypes of electrodes, one or more ablation electrodes and one or moredigestion electrodes. The two types of electrodes are independentlycoupled to opposite poles of the power supply so that current can flowtherebetween. In one embodiment, the ablation electrode(s) are adaptedfor aggressively removing tissue, including cartilage tissue, from aregion of tissue to be treated; and the ablation electrode(s) areadapted for breaking down tissue fragments, e.g. resected tissuefragments dislodged by the ablation electrode(s), into smaller fragmentsor low molecular weight ablation by-products. Both the ablation anddigestion electrodes are adapted for performing tissue ablation in acool ablation process, i.e., a plasma is generated in the presence of anelectrically conductive fluid, and the plasma induces moleculardissociation of high molecular weight tissue components into lowmolecular weight by-products. During such a process, the tissue treatedor removed may be exposed to a temperature generally not exceeding 90°C., and typically in the range of from about 45° to 90° C., moretypically from about 55° to 75° C.

The power supply may be, for example, power supply 428 (FIG. 7).Preferably, the power supply to which the probe is coupled is capable ofproviding to the probe a high frequency (e.g., RF) voltage of a selectedvoltage level and frequency. The selected voltage frequency is typicallybetween about 5 kHz and 20 MHz, essentially as described hereinabove.The RMS voltage will usually be in the range of from about 5 volts to1000 volts, and the peak-to-peak voltage will be in the range of fromabout 10 to 2000 volts, again as described hereinabove. Step 1902involves positioning the probe adjacent to target tissue. For example,the probe distal end may be advanced towards target tissue such that theablation electrode is in the vicinity of the tissue at the site targetedfor treatment. By way of a more specific example, the ablation electrodemay be brought adjacent to the meniscus during arthroscopic surgery ofthe knee. In one aspect, the probe may be positioned with respect totarget tissue such that the ablation electrode is in contact with tissueat the target site, while the digestion electrode is not in contact withthe tissue at the target site. In one embodiment, the digestionelectrode may be located substantially proximal to the ablationelectrode, such that when the ablation electrode is in the presence ofthe tissue at the target site, the digestion electrode is somewhatdistant from the tissue at the target site. For example, the ablationelectrode may be positioned terminally on the shaft or near the terminusof the shaft, while the digestion electrode may be positioned within theaspiration lumen.

Step 1904 involves supplying power from the power supply to the ablationelectrode. Typically, when the ablation electrode is in the presence oftissue, the power supply preferentially supplies power to the ablationelectrode, and under these circumstances the ablation electrodegenerally serves as active electrode. (During a different phase or stepof the procedure, the ablation electrode may undergo a reversal of rolesto function as a return electrode (step 1912)). Supplying power of asuitable frequency and voltage to the ablation electrode in the presenceof an electrically conductive fluid causes a plasma to be generated inthe vicinity of the ablation electrode. The plasma generated leads tothe localized removal of tissue via a cool ablation mechanism(Coblation®), as described hereinabove. In one embodiment, step 1904involves preferentially supplying power from the power supply to theablation electrode, largely to the exclusion of the digestion electrode.That is to say, at any given time point, power from the power supply issupplied preferentially to one or the other of the two types ofelectrodes, such that the ablation electrode (or the digestionelectrode, step 1912) may receive up to about 100% of the power from thepower supply. In this way, the power available from the power supply isused efficiently by the electrode which receives the power (i.e., theelectrode functioning as the active electrode) for the aggressivegeneration of a plasma and ablation of tissue.

Optional step 1906 involves delivering an electrically conductive fluid,e.g., isotonic saline, a gel, etc., to the target site or to theablation electrode. In a wet field procedure, wherein an electricallyconductive fluid is already present, step 1906 may be omitted. Step 1906may be performed before, during, or after the performance of step 1904.Also, step 1906 may be repeated as often as is appropriate during thecourse of a surgical procedure. Step 1906 may be achieved by deliveringan electrically conductive fluid via a fluid delivery device which isintegral with the electrosurgical probe, or via an ancillary device.Step 1908 involves removing tissue from the target site with theablation electrode via a cool ablation mechanism of the invention. Step1908 leads to molecular dissociation of tissue components and results inthe formation of low molecular weight by-products. Depending on thenature of the tissue, the voltage level, and other parameters, step 1908may also result in the formation of resected tissue fragments. In oneembodiment, step 1908 involves aggressively removing tissue from thetarget site such that tissue fragments may be resected from the targetsite by the ablation electrode due, at least in part, to the generationof an aggressive plasma in the vicinity of the target site (step 1904).

Step 1910 involves aspirating materials from the target site. Materialsthus aspirated may include electrically conductive body fluids (e.g.,synovial fluid, blood), extrinsic electrically conductive fluids (e.g.,isotonic saline supplied in step 1906), and resected tissue fragments.Such materials may be aspirated from the target site via an aspirationdevice integral with the electrosurgical probe, as describedhereinabove. The aspirated materials which pass from the target sitethrough the aspiration device constitute an aspiration stream.

Step 1912 involves supplying power to the digestion electrode. In oneembodiment, step 1912 involves supplying power to the digestionelectrode largely to the exclusion of the ablation electrode. That is tosay, during step 1912 up to about 100% of the power from the powersupply may be supplied to the digestion electrode. Under thesecircumstances, the digestion electrode serves as an active electrode,and the ablation electrode serves as a return electrode. Typically, thedigestion electrode preferentially receives power from the power supplyunder circumstances where the digestion electrode is in the presence oftissue, for example, one or more resected tissue fragments in theaspiration stream adjacent to the digestion electrode.

Step 1914 involves ablating any resected tissue fragments present in theaspiration stream to form low molecular weight ablation by-products.Typically, the digestion electrode is arranged in relation to theaspiration device such that the aspiration stream contacts the digestionelectrode. For example, the digestion electrode may be adjacent to orproximal to an aspiration port, or the digestion electrode may belocated within an aspiration lumen. Typically, ablation of resectedtissue fragments is accomplished by the digestion electrode in a coolablation process, as described hereinabove. In one embodiment, theelectrosurgical system may be triggered to “switch” power from theablation electrode to the digestion electrode by changes in electricalimpedance in the aspiration stream in the vicinity of the digestionelectrode. Such localized changes in impedance may result from theproximity of resected tissue fragments to the digestion electrode.Triggering a switch in the power away from the ablation electrode and tothe digestion electrode may be dependent on the surface area ratio ofthe ablation and digestion electrodes. In one aspect of the invention,steps 1912, 1914 represent a transient, intermittent phase of operationof the electrosurgical system/probe. For example, immediately after thecompletion of step 1914, the ablation electrode may resume its role asactive electrode, and concomitantly therewith the digestion electrodemay revert to its role as return electrode. For instance, in the absenceof resected tissue fragments in the vicinity of the digestion electrode,the power may be switched away from the digestion electrode and insteadthe power may be supplied preferentially to the ablation electrode. Inthis way, once power to the probe has been turned on by the operator(surgeon), steps 1904 and 1908 through 1912 may be repeated numeroustimes in rapid succession during the course of a surgical procedure,without operator intervention or input. As already noted above, step1906 may also be repeated as appropriate.

Other modifications and variations can be made to disclose embodimentswithout departing from the subject invention as defined in the followingclaims. For example, with regard to the electrosurgical probe having afluid delivery device, the fluid delivery port can be positioned in theelectrode support such that the electrically conductive fluid will bedelivered directly to the ablation electrode(s).

While the exemplary embodiments of the present invention have beendescribed in detail, by way of example and for clarity of understanding,a variety of changes, adaptations, and modifications will be obvious tothose of skill in the art. Therefore, the scope of the present inventionis limited solely by the appended claims.

What is claimed is:
 1. An electrosurgical apparatus for removing tissuefrom a target site, comprising: a probe including a first electrode typeand a second electrode type, wherein the first electrode type and thesecond electrode type alternate between serving as an active electrodeand serving as a return electrode, such that when the first electrodetype serves as the active electrode the second electrode type serves asthe return electrode, and when the second electrode type serves as theactive electrode the first electrode type serves as the returnelectrode.
 2. The apparatus of claim 1, wherein the probe consistsessentially of an ablation electrode and a digestion electrode.
 3. Theapparatus of claim 1, wherein the first electrode type and the secondelectrode type are independently coupled to opposite poles of a powersupply for supplying alternating current between the first electrodetype and the second electrode type, and at any given time point thepower supply alternatively supplies electric power preferentially to thefirst electrode type or preferentially to the second electrode type. 4.The apparatus of claim 1, wherein the first electrode type comprises anablation electrode and the second electrode type comprises a digestionelectrode, and the electrosurgical apparatus lacks a dedicated returnelectrode.
 5. The apparatus of claim 4, wherein the ablation electrodeand the digestion electrode have surface areas Sa and Sd, respectively,and the ratio Sa:Sd is in the range of from about 3:1 to about 1:1. 6.The apparatus of claim 5, wherein the ratio Sa:Sd is in the range offrom about 2.5:1 to about 1.5:1.
 7. The apparatus of claim 1, whereinthe probe includes a shaft having a shaft distal end portion and a shaftproximal end portion, and the first electrode type comprises an ablationelectrode disposed on an electrode support located at the shaft distalend portion.
 8. The apparatus of claim 7, wherein the probe includes anaspiration device including an aspiration port, and the ablationelectrode is located distal to the aspiration port.
 9. The apparatus ofclaim 8, wherein the ablation electrode at least partially surrounds adistal portion of the aspiration port.
 10. The apparatus of claim 8,wherein the ablation electrode comprises a substantially semi-circularshaped screen.
 11. The apparatus of claim 4, wherein the probe includesa shaft having a shaft distal end portion, and an aspiration devicehaving an aspiration lumen terminating distally at an aspiration port,the aspiration port arranged on the shaft distal end portion, and thedigestion electrode arranged within the aspiration lumen.
 12. Theapparatus of claim 1, wherein the second electrode type comprises adigestion electrode, and the digestion electrode comprises a metalribbon or a flat wire.
 13. The apparatus of claim 4, wherein the probeincludes a shaft, the digestion electrode comprises a first end coupledto a digestion electrode lead and a second end terminating within theshaft, wherein the digestion electrode is coupled to a high frequencypower supply via the digestion electrode lead, and the second end iselectrically insulated.
 14. The apparatus of claim 1, wherein the firstelectrode type and the second electrode type are coupled to oppositepoles of a high frequency power supply for supplying electrical powerthereto, the probe is capable of resecting tissue fragments andaspirating resected tissue fragments, the second electrode typepreferentially receives power from the power supply only when the secondelectrode type is in the presence of tissue.
 15. The apparatus of claim3, wherein, in the absence of tissue in the vicinity of the secondelectrode type, the first electrode type and the second electrode typeserve as active electrode and return electrode, respectively.
 16. Theapparatus of claim 3, wherein the first electrode type comprises anablation electrode capable of removing tissue from the target site by acool ablation process to generate resected tissue fragments, wherein thetissue at the target site is exposed to a temperature in the range offrom about 45° to about 90° C., the second electrode type comprises adigestion electrode capable of aggressively ablating the resected tissuefragments, and the digestion electrode preferentially receives electricpower only in the presence of at least one of the resected tissuefragments.
 17. The apparatus of claim 1, wherein the first electrodetype and the second electrode type each comprise a material selectedfrom the group consisting of: tungsten, stainless steel alloys, platinumor its alloys, titanium or its alloys, molybdenum or its alloys, nickelor its alloys, gold, aluminum, and copper.
 18. The apparatus of claim 1,wherein at least one of the first electrode type and the secondelectrode type consists essentially of platinum.
 19. The apparatus ofclaim 1, wherein the probe includes a shaft, and the shaft is coveredwith an electrically insulating material or constitutes an electricallyinsulating material.
 20. The apparatus of claim 4, wherein the probeincludes a shaft having a shaft distal end portion and an electrodesupport disposed on the shaft distal end portion, and the ablationelectrode is affixed to the electrode support via a plurality of ballwires.
 21. The apparatus of claim 4, wherein the ablation electrode isaffixed to an electrode support comprising a material selected from thegroup consisting of a ceramic, a glass, and a silicone.
 22. Theapparatus of claim 3, wherein the electric power supplied by the powersupply comprises a high frequency voltage characterized by apeak-to-peak voltage in the range of from about 10 to 2000 volts, a RMSvoltage in the range of from about 5 volts to 1000 volts, and afrequency in the range of from about 5 kHz to 20 MHz.
 23. The apparatusof claim 1, further comprising a fluid delivery device having a fluiddelivery port in communication with a fluid delivery lumen, the fluiddelivery port distal to the first electrode type, and the firstelectrode type comprises at least one ablation electrode.
 24. Anelectrosurgical system for removing tissue from a target site,comprising: a probe, and a high frequency power supply coupled to theprobe for supplying electric power to the probe, the probe including: ashaft having a shaft distal end portion and a shaft proximal endportion; an ablation electrode located at the shaft distal end portion,the ablation electrode independently coupled to a first pole of the highfrequency power supply; an aspiration device including an aspirationport in communication with an aspiration lumen, the aspiration portlocated at the shaft distal end portion; and a digestion electrodeindependently coupled to a second pole of the high frequency powersupply, wherein the high frequency power supply alternates betweensupplying up to about 100% of the electric power to the ablationelectrode and supplying up to about 100% of the electric power to thedigestion electrode.
 25. The electrosurgical system of claim 24, whereinalternating between supplying up to about 100% of the electric power tothe ablation electrode and supplying up to about 100% of the electricpower to the digestion electrode is determined by the presence orabsence of tissue in the vicinity of the ablation electrode and thedigestion electrode.
 26. The electrosurgical system of claim 24, whereinalternating between supplying up to about 100% of the electric power tothe ablation electrode and supplying up to about 100% of the electricpower to the digestion electrode is determined by the electricalimpedance of the milieu of the digestion electrode.
 27. Theelectrosurgical system of claim 24, wherein alternating betweensupplying up to about 100% of the electric power to the ablationelectrode and supplying up to about 100% of the electric power to thedigestion electrode is dependent on the ratio of the surface area of theablation electrode to the surface area of the digestion electrode and isdetermined by the electrical impedance of the milieu of the digestionelectrode.
 28. The electrosurgical system of claim 24, wherein the ratioof the surface area of the ablation electrode to the surface area of thedigestion electrode is in the range of from about 3:1 to about 1:1. 29.The electrosurgical system of claim 24, wherein the ratio of the surfacearea of the ablation electrode to the surface area of the digestionelectrode is in the range of from about 2.5:1 to about 1.5:1.
 30. Theelectrosurgical system of claim 24, wherein the electrosurgical systemlacks a dedicated return electrode.
 31. The electrosurgical system ofclaim 24, wherein, in the presence of an electrically conductive fluid,both the ablation electrode and the digestion electrode effectivelygenerate a plasma upon application of a high frequency voltage thereto,and both the ablation electrode and the digestion electrode are capableof aggressively breaking down tissue via a cool ablation process,wherein tissue components undergo molecular dissociation, and the tissuewhich undergoes molecular dissociation is exposed to a temperature notexceeding 90° C.
 32. The electrosurgical system of claim 31, wherein thehigh frequency voltage is characterized by a peak-to-peak voltage in therange of from about 10 to 2000 volts, a RMS voltage in the range of fromabout 5 volts to 1000 volts, and a frequency in the range of from about5 kHz to 20 MHz.
 33. The electrosurgical system of claim 24, furthercomprising an aspiration device having an aspiration port incommunication with an aspiration lumen, the digestion electrode disposedadjacent to the aspiration port or within the aspiration lumen.
 34. Theelectrosurgical system of claim 24, wherein the ablation electrode isdisposed terminally on the shaft or laterally on the shaft.
 35. Anelectrosurgical probe capable of removing tissue from a target site andadapted for connection to a power supply, the electrosurgical probecomprising: a shaft having at least one ablation electrode and at leastone digestion electrode, the at least one ablation electrode and the atthe least one digestion electrode independently coupled to oppositepoles of the power supply, wherein the at least one ablation electrodecan serve as an active electrode or a return electrode, and the at theleast one digestion electrode can serve as the active electrode or thereturn electrode.
 36. The electrosurgical probe of claim 35, wherein theat the least one digestion electrode serves as the return electrode whenthe at least one ablation electrode serves as the active electrode, andthe at least one ablation electrode serves as the return electrode whenthe at the least one digestion electrode serves as the active electrode.37. The electrosurgical probe of claim 35, wherein the at least oneablation electrode serves as a primary active electrode, and the at theleast one digestion electrode serves as a secondary active electrode.38. The electrosurgical probe of claim 35, wherein the at least oneablation electrode serves as the active electrode when the at least oneablation electrode is in the presence of tissue while the at least onedigestion electrode is not in the presence of tissue.
 39. Theelectrosurgical probe of claim 35, wherein the at the least onedigestion electrode serves as the active electrode when the at least onedigestion is in the presence of tissue while the at least one ablationelectrode is not in the presence of tissue.
 40. The electrosurgicalprobe of claim 35, wherein when both the at least one ablation electrodeand the at least one digestion electrode are in the presence of tissue,preferential delivery of electric power from the power supply to eitherthe at least one ablation electrode or to the at least one digestionelectrode is dependent on the ratio of the surface area of the at leastone ablation electrode to the surface area of the at least one digestionelectrode.
 41. The electrosurgical probe of claim 40, wherein the ratioof the surface area of the at least one ablation electrode to thesurface area of the at least one digestion electrode is in the range offrom about 3:1 to about 1:1.
 42. The electrosurgical probe of claim 35,wherein during a given time period of operation of the probe, the atleast one ablation electrode or the at least one digestion electrodepreferentially or exclusively receives power from the power supply. 43.The electrosurgical probe of claim 35, wherein the at least one ablationelectrode functions as the active electrode when the at least oneablation electrode preferentially or exclusively receives power from thepower supply, and the at least one digestion electrode functions as thereturn electrode when the at least one ablation electrode preferentiallyor exclusively receives power from the power supply.
 44. Theelectrosurgical probe of claim 35, wherein the at least one digestionelectrode functions as the active electrode when the at least onedigestion electrode preferentially or exclusively receives power fromthe power supply, and the at least one ablation electrode functions asthe return electrode when the at least one digestion electrodepreferentially or exclusively receives power from the power supply. 45.The electrosurgical probe of claim 35, wherein during a first mode ofoperation of the probe the ablation electrode receives from about 60% toabout 100% of the power from the power supply, and during a second modeof operation of the probe the digestion electrode receives from about60% to about 100% of the power from the power supply.
 46. Theelectrosurgical probe of claim 45, wherein the first mode of operationof the probe is longer than the second mode of operation of the probe,the first mode of operation of the probe precedes the second mode ofoperation of the probe, and wherein the first mode of operation of theprobe and the second mode of operation of the probe are repeatedsequentially.
 47. The electrosurgical probe of claim 35, wherein the atleast one ablation electrode comprises a material selected from thegroup consisting of tungsten, stainless steel alloys, platinum or itsalloys, titanium or its alloys, molybdenum or its alloys, nickel or itsalloys, gold, aluminum, and copper.
 48. The electrosurgical probe ofclaim 35, wherein the at least one ablation electrode is mountedlaterally on the shaft or mounted terminally on the shaft.
 49. Theelectrosurgical probe of claim 35, wherein the at least one ablationelectrode at least partially surrounds an aspiration port.
 50. Theelectrosurgical probe of claim 35, wherein the at least one ablationelectrode is disposed substantially distal to an aspiration port. 51.The electrosurgical probe of claim 35, wherein the at least onedigestion electrode is disposed proximal to an aspiration port.
 52. Theelectrosurgical probe of claim 35, wherein the at least one digestionelectrode comprises a material selected from the group consisting oftungsten, stainless steel alloys, platinum or its alloys, titanium orits alloys, molybdenum or its alloys, nickel or its alloys, gold,aluminum, and copper.
 53. The electrosurgical probe of claim 35, whereinthe at least one digestion electrode comprises a first end coupled to adigestion electrode lead and a second free end, the digestion electrodelead for delivering electric power from the power supply, and the freeend does not contact an electrically conductive material.
 54. Theelectrosurgical probe of claim 35, wherein the at least one digestionelectrode comprises a first free end which terminates in an electricallyinsulating material.
 55. The electrosurgical probe of claim 53, whereinthe at least one digestion electrode comprises a metal ribbon.
 56. Theelectrosurgical probe of claim 35, wherein the probe further consistsessentially of an aspiration device having an aspiration port leading toan aspiration lumen, and the at least one digestion electrode isdisposed adjacent to the aspiration port or arranged within theaspiration lumen.
 57. The electrosurgical probe of claim 35, wherein theprobe lacks a dedicated return electrode.
 58. A method of treating atissue to be treated at a target site with an electrosurgical system,the electrosurgical system including a probe having an ablationelectrode and a digestion electrode, the ablation electrode and thedigestion electrode independently coupled to opposite poles of a powersupply, and the method comprising: a) positioning the ablation electrodein the presence of the tissue to be treated; b) preferentially supplyingelectric power from the power supply to the ablation electrode; and c)alternatively to said step b), preferentially supplying electric powerfrom the power supply to the digestion electrode.
 59. The method ofclaim 58, wherein said step b) is performed before said step c).
 60. Themethod of claim 58, wherein during said step b) the ablation electrodeserves as a first active electrode and the digestion electrode serves asa first return electrode.
 61. The method of claim 58, wherein duringsaid step c) the digestion electrode serves as a second active electrodeand the ablation electrode serves as a second return electrode.
 62. Themethod of claim 58, further comprising the step of: d) prior to saidsteps b) and c), selecting a power level to be supplied from the powersupply, wherein said step b) comprises supplying up to about 100% of theselected power level from the power supply to the ablation electrode,and said step c) comprises supplying up to about 100% of the selectedpower level from the power supply to the digestion electrode.
 63. Themethod of claim 58, further comprising repeatedly alternating betweensaid step b) and said step c).
 64. The method of claim 63, whereinrepeatedly alternating between said steps b) and c) is inherent in theelectrosurgical system and is dependent on the presence or absence oftissue at the ablation electrode and the digestion electrode.
 65. Themethod of claim 64, wherein repeatedly alternating between said steps b)and c) is dependent on a change in electrical impedance in the vicinityof the ablation electrode or the digestion electrode.
 66. The method ofclaim 58, wherein a switch from said step b) to said step c) is inducedby the presence of tissue in an electrically conductive fluid in thevicinity of the digestion electrode.
 67. The method of claim 58, whereina switch from said step c) to said step b) is induced by the absence oftissue in an electrically conductive fluid in the vicinity of thedigestion electrode while the ablation electrode is in the presence oftissue.
 68. The method of claim 58, wherein the ratio of the surfacearea of the ablation electrode to the surface area of the digestionelectrode is in the range of from about 2.5:1 to about 1.5:1.
 69. Themethod of claim 58, wherein said step b) results in generation of aplasma in the vicinity of the ablation electrode and removal of at leasta portion of the tissue from the target site in a cool ablation process,wherein the tissue at the target site is exposed to a temperature in therange of from about 45° C. to about 90° C.
 70. The method of claim 58,wherein said step c) results in generation of a plasma in the vicinityof the digestion electrode and the plasma induces molecular dissociationof tissue components of at least one tissue fragment in the vicinity ofthe digestion electrode to yield low molecular weight ablationby-products.
 71. The method of claim 58, wherein at any given time pointsaid step b) and said step c) are mutually exclusive.
 72. The method ofclaim 58, wherein said step b) defines an ablation mode, and said stepc) defines an alternative digestion mode.
 73. The method of claim 58,wherein said step a) comprises positioning the ablation electrodeadjacent to, or in contact with, cartilage tissue, and said step b)results in removal of at least a portion of the cartilage tissue. 74.The method of claim 58, further comprising the step of delivering anelectrically conductive fluid to the ablation electrode or to the tissueat the target site.
 75. The method of claim 58, further comprising thestep of aspirating resected tissue from the target site in an aspirationstream, wherein the aspiration stream contacts the digestion electrode.76. The method of claim 58, wherein the electric power supplied to theablation electrode and to the digestion electrode is characterized by apeak-to-peak voltage in the range of from about 10 to 2000 volts, and aRMS voltage in the range of from about 5 volts to 1000 volts.
 77. Amethod of removing tissue from a target site with an electrosurgicalprobe, the method comprising: a) coupling the electrosurgical probe to apower supply, wherein the electrosurgical probe includes a firstelectrode type and a second electrode type, and the first electrode typeand the second electrode type are independently coupled to oppositepoles of the power supply; b) preferentially supplying power from thepower supply to the first electrode type; and c) in response to a changein electrical impedance experienced by the first electrode type or thesecond electrode type, preferentially supplying power from the powersupply to the second electrode type.
 78. The method of claim 77, whereinthe first electrode type and the second electrode type alternate betweenserving as an active electrode and serving as a return electrode. 79.The method of claim 77, wherein the first electrode type comprises atleast one ablation electrode, and said step b) results in resection oftissue fragments, and the method further comprises aspirating theresected tissue fragments from the target site in an aspiration stream.80. The method of claim 79, wherein the second electrode type comprisesat least one digestion electrode, the at least one digestion electrodeis in contact with the aspiration stream, and the change in electricalimpedance results from movement of a resected tissue fragment in theaspiration stream towards the at least one digestion electrode.
 81. Themethod of claim 77, wherein the ratio of the surface area of the firstelectrode type to the surface area of the second electrode type is inthe range of from about 3:1 to about 1:1.
 82. The method of claim 77,wherein said step b) results in localized generation of a plasma in thevicinity of the first electrode type and removal of tissue from thetarget site, wherein tissue at the target site is exposed to atemperature in the range of from about 45° to 90° C.
 83. The method ofclaim 77, wherein during said step b) the first electrode type receivesfrom about 60% to about 100% of the power from the power supply, andduring said step c) the second electrode type receives from about 60% toabout 100% of the power from the power supply.
 84. An electrosurgicalsystem for treating tissue at a target site, comprising: anelectrosurgical probe including a first electrode type and a secondelectrode type, wherein both the first electrode type and the secondelectrode type are adapted for having an electrically-inducedtissue-altering effect, and the electrosurgical probe is configured suchthat the first electrode type can be brought into contact with thetissue at the target site while the second electrode type does notcontact the tissue at the target site.
 85. The system of claim 84,wherein the second electrode type is remote from the tissue at thetarget site when the first type of electrode is in contact with thetissue at the target site.
 86. The system of claim 84, wherein the firstelectrode type comprises at least one ablation electrode and the secondelectrode type comprises at least one digestion electrode.
 87. Thesystem of claim 84, further comprising a power supply, the firstelectrode type and the second electrode type independently coupled toopposite poles of the power supply, and the power supply adapted forindependently supplying a high frequency AC voltage to the firstelectrode type and the second electrode type.
 88. The system of claim87, wherein one of the first electrode type and the second electrodetype preferentially receives the power from the power supply.
 89. Thesystem of claim 88, wherein the first electrode type or the secondelectrode type receives up to about 100% of the power from the powersupply.
 90. The system of claim 87, wherein during a first mode ofoperation of the electrosurgical system the first electrode typepreferentially receives the power from the power supply and during asecond mode of operation of the electrosurgical system the secondelectrode type preferentially receives the power from the power supply.91. The system of claim 84, wherein during a first mode of operation ofthe electrosurgical system the first electrode type receives from about70% to about 100% of the power from the power supply and during a secondmode of operation of the electrosurgical system the second electrodetype receives from about 70% to about 100% of the power from the powersupply.
 92. An electrosurgical system, comprising: a probe including afirst electrode type and a second electrode type, wherein both the firstelectrode type and the second electrode type are adapted for having atissue-altering effect, and wherein during a first mode of operation ofthe electrosurgical system the first electrode type functions as anactive electrode while the second electrode type functions as a returnelectrode, and during a second mode of operation of the electrosurgicalsystem the second electrode type functions as the active electrode whilethe first electrode type functions as the return electrode.
 93. Theelectrosurgical system of claim 92, wherein the first electrode typecomprises an ablation electrode adapted for ablation of tissue at atarget site and the second electrode type comprises a digestionelectrode adapted for digesting tissue fragments, and the probe isconfigured such that the digestion electrode avoids contact with thetissue at the target site when the ablation electrode is in contact withthe tissue at the target site.
 94. The electrosurgical system of claim92, further comprising a power supply for supplying electric power tothe probe, the first electrode type and the second electrode typeindependently coupled to opposite poles of the power supply, whereinduring the first mode of operation of the electrosurgical system thefirst electrode type receives from about 60% to about 100% of the powerfrom the power supply, and during the second mode of operation of theelectrosurgical system the second electrode type receives from about 60%to about 100% of the power from the power supply.
 95. Theelectrosurgical system of claim 92, wherein during use of theelectrosurgical system, the first electrode type and the secondelectrode type alternately function as the active electrode.
 96. Theelectrosurgical system of claim 92, wherein, during use of theelectrosurgical system, the electrosurgical system alternates betweenthe first mode of operation and the second mode of operation.
 97. Theelectrosurgical system of claim 92, wherein the tissue-altering effectcomprises cool ablation of tissue and the tissue which undergoes thetissue-altering effect is exposed to a temperature in the range of fromabout 45° C. to about 90° C.
 98. The electrosurgical system of claim 92,wherein the first electrode type is adapted for cool ablation of tissueat a target site.
 99. The electrosurgical system of claim 92, whereinthe second electrode type is adapted for cool ablation of tissuefragments resected from a target site.